COLLABORATIVE RESEARCH & FORECASTING

Adhikari, P., Y. Hong, K. R. Douglas, D. B. Kirschbaum, J. J. Gourley, R. F. Adler, G. R. Brakenridge, 2010: A digitized global flood inventory (1998-2008): Compilation and preliminary results. J. Natural Hazards, 55, 405-422.

Anderson, C. J., R. W. Arritt, J. S. Kain, 2007: An alternative mass flux profile in the Kain-Fritsch convective parameterization and its effect on seasonal precipitation.. J. Hydrometeor, 8, 1128-1140.

Baldwin, M. E., J. S. Kain, 2006: Sensitivity of Several Performance Measures to Displacement Error, Bias, and Event Frequency. Weather and Forecasting, 21, 636-648.

The sensitivity of various accuracy measures to displacement error, bias, and event frequency is analyzed for a simple hypothetical forecasting situation. Each measure is found to be sensitive to displacement error and bias, but probability of detection and threat score do not change as a function of event frequency. On the other hand, equitable threat score, true skill statistic, and odds ratio skill score behave differently with changing event frequency. A newly devised measure, here called the bias-adjusted threat score, does not change with varying event frequency and is reletively insensitive to bias. Numerous plots are presented to allow users of these accuracy measures to make quantitative estimates of sensitivities that are relevant to their particular application.

Available online at http://available soon from AMS.

Beida, R., M. W. Douglas, 2010: Developing high spatial resolution daytime cloud climatologies for Africa. Extended Abstracts, 29th Conference on Hurricanes and Tropical Meteorology, Tucson, AZ, USA, American Meteorological Society, P2.23.

MODIS visible imagery has been used to develop a short-period climatology of cloudiness for the African continent at approximately 250m spatial resolution. The MODIS imagery, from satellite overpasses at ~ 1030 and 1330 Local Time, are used to produce frequencies of visible clouds that provide a good estimate of mid-day cloudiness. Though our means fields are based on only about 5 years of data, they depict strong mesoscale controls on the mean cloudiness. Over much of Africa these controls are independent of season and are evident in the monthly means of any year. Most patterns can be explained as the effects of diurnally-driven circulations associated with sloping topography or land-water contrasts. Some regions with frequent cloudiness reflect the interaction of the prevailing winds with topography. This cloud climatology should be of value to all forecasters in Africa who wish to understand better their regional and local climatology.

Available online at http://ams.confex.com/ams/29Hurricanes/techprogram/MEETING.HTM.

Brooks, H. E., 2006: A global view of severe thunderstorms: Estimating the current distribution and possible future changes. Preprints, Symposium on the Challenges of Severe Convective Storms, Atlanta, GA, USA, American Meteorological Society, CD-ROM, J4.2.

Brooks, H. E., A. R. Anderson, K. Riemann, I. Ebbers, H. Flachs, 2007: Climatological aspects of convective parameters from the NCAR/NCEP reanalysis. Atmospheric Research, 83, 294-305.

Annual cycles of convectively important atmospheric parameters have been computed for a variety of from the National Center for Atmospheric Research (NCAR)/National Centers for Environmental Prediction (NCEP) global reanalysis, using 7 years of reanalysis data. Regions in the central United States show stronger seasonality in combinations of thermodynamic parameters than found elsewhere in North America or Europe. As a result, there is a period of time in spring and early summer when climatological mean conditions are supportive of severe thunderstorms.
The annual cycles help in understanding the large-scale processes that lead to the combination of atmospheric ingredients necessary for strong convection. This, in turn, lays groundwork for possible changes in distribution of the environments associated with possible global climate change.

Available online at http://www.nssl.noaa.gov/users/brooks/public_html/papers/ECSS2004.pdf.

Brooks, H. E., 2007: Development and use of climatologies of convective weather. Atmospheic Convection: Research and Operational Forecasting Aspects, D. B. Gaiotti, R. Steinacker, F. Stel, Ed(s)., SpringerWienNew York, 123-132.

Estimates of the occurrence (“climatologies”) of convective phenomena in time, space, and intensity can be useful in a variety of contexts. They provide background for forecasters, and the risk management and meteorological research communities. In part, because of the different needs of those user groups, caution must be applied when developing and using climatologies, especially if the intended application is outside of the original intent of the developers.

Brooks, H. E., 2007: Environmental conditions associated with convective phenomena: Proximity soundings. Atmospheic Convection: Research and Operational Forecasting Aspects, D. B. Gaiotti, R. Steinacker, F. Stel, Ed(s)., SpringerWeinNewYork, 113-122.

An important tool in understanding the relationship between environments and observed severe thunderstorm events are vertical profiles of environmental conditions collected in the vicinity of the storms. These relationships can help in the future forecasting of weather. In this paper, the use and cautions associated with these so-called proximity soundings are discussed.

Brooks, H. E., 2007: Ingredients-based forecasting. Atmospheric Convection: Research and Operational Forecasting Aspects, D. B. Gaiotti, R. Steinacker, Ed(s)., SpringerWienNew York, 133-140.

Forecasting the weather can be thought of as a problem in extracting a small signal from a noisy background field. Much information is available to the forecaster, but, frequently, only a small amount of that information is of importance for solving the forecast problem(s) of the day. As a result, an approach to forecasting must maximize the efficiency of the process. An effective way, particularly for hazardous weather, is to identify the ingredients required to produce a particular weather event and then to focus on the processes that can affect the presence of those ingredients. This allows the forecaster to narrow the range of aspects of the observations and model guidance that are considered during the forecast shift and, it is hoped, identify crucial developments as they occur.

Brooks, H. E., 2007: Practical Aspects of Forecasting Severe Convection in the United States: Environmental Conditions and Initiation. Atmospheic Convection: Research and Operational Forecasting Aspects, D. B. Gaiotti, R. Steinacker, F. Stel, Ed(s)., SpringerWienNew York, 141-148.

The first stage of forecasting convective weather involves forecasting the evolution of conditions that are favorable for the development of storms and their probable initiation. The scale of the forecasts are typically on the order of 100 km or larger and the lead time between the forecast and storms is 1-48 hours. In the United States, procedures have evolved so that the Storm Prediction Center of the National Weather Service has the responsibility for issuing these forecasts for the contiguous 48 states (the part of the US excluding Alaska and Hawaii.)

Brooks, H. E., 2007: Practical Aspects of Forecasting Severe Convection in the United States: Storm Evolution and Warning. Atmospheic Convection: Research and Operational Forecasting Aspects, D. B. Gaiotti, R. Steinacker, F. Stel, Ed(s)., SpringerWienNew York, 149-156.

In order to protect life and property, forecasts of severe convection are critical on short time and space scales (on the order of 1 hour or less and a few 10s of km or less). Accurate assessment of the environment and monitoring of high-resolution observational data, frequently focusing on radar-observed evolution, are essential in this process. In the United States, these short-term time and space scale forecasts are referred to as warnings and are prepared by local forecast offices of the National Weather Service, who have responsibility for forecasters on the order of 100,000 km2.

Brooks, H. E., C. A. Doswell III, D. Sutter, 2008: Low-Level Winds in Tornadoes and Potential Catastrophic Tornado Impacts in Urban Areas. Bulletin of the American Meteorological Society, 89, 87-90.

Brooks, H. E., N. Dotzek, 2008: The spatial distribution of severe convective storms and an analysis of their secular changes. Climate Extremes and Society, H. F. Diaz, Ed(s)., Cambridge University Press, 35-54.

Severe convective storms are responsible for billions of US dollars in damage each year around the world. They form an important part of the climate system by redistributing heat, moisture, and trace gases, as well as producing large quantities of precipitation.

Reporting of severe convection varies from country to country, however, so that determining their distribution from the reports alone is difficult, at best. Evidence does exist that the intensity of some events, particularly tornadoes, follows similar distributions in different locations, making it possible to build statistical models of occurrence. Remotely-sensed observations provide some insight, but the relationship between the observable parameters and the actual events of interest limits the quality of the estimate. Another approach is to use observations of the larger-scale environments.

As has been stated, the relationship between the observation and the event limits the estimate, but global coverage is possible. Time series of the favorable environments can also be developed from such data. In order to improve the estimates, the most pressing need is better observational data of events. Very few countries have formal systems for collection of severe thunderstorm reports. A new effort from a consortium of researchers in Europe to develop a continental-wide database offers the possibility of a significant improvement in data in that part of the world.

Brooks, H. E., 2008: Extreme Weather: Understanding the Science of Hurricanes, Tornadoes, Floods, Heat Waves, Snow Storms, Global Warming and Other Atmospheric Disturbances. EOS, Transactions American Geophysical Union, 89, 258-258.

Extreme weather is of importance because of the threats it makes to life and property. At the same time, extreme weather is a great fascination for meteorologists as well as for the general public. The conditions and processes that lead to extreme weather—although governed by the same physical principles as “ordinary” weather—frequently are far from the average state of the atmosphere. Thus, explaining them in simple terms can be difficult. This book represents an effort to explain the development of extreme weather to the public.

Brooks, H. E., 2009: Proximity soundings for severe convection for Europe and the United States from reanalysis data. Atmospheric Research, 93, 546-553.

Proximity soundings from reanalysis data have been created for significant severe thunderstorms in the United States and Europe, along with corresponding soundings not associated with severe thunderstorms. The probability of a combination of convective available potential energy (CAPE) and deep tropospheric wind shear being associated with significant severe thunderstorms has been calculated for both areas. Probabilities of significant severe storms are higher for high CAPE and shear in Europe, but those large scale environmental conditions are experienced much more frequently in the US, so that the overall number of events is much higher in the US. Probabilities of significant storms are approximately constant for constant values of CAPElow asteriskShear for each of the datasets. High values of 0–1 km wind shear and low lifted condensation levels are associated with higher probabilities that significant severe thunderstorms will be associated with significant tornadoes.

A subset of the US data, taken from the southeastern US in the cool season, produces probabilities that are much closer to the European values than the overall US data. The environments also are closer to European values with relatively low CAPE and low lifted condensation levels. From the southeastern US data, it is shown that the probability of severe convection occurring with moderate values of CAPElow asteriskShear is much higher in the cool season than in the warm season. It is suggested that the higher probabilities result from stronger synoptic forcing and stronger and more frequent boundaries to initiate convection.

Brooks, H. E., P. T. Marsh, A. M. Kowaleski, P. Groenemeijer, T. E. Thompson, C. S. Schwartz, C. M. Shafer, A. Kolodziej, N. Dahl, D. Buckey, 2011: Evaluation of European Storm Forecast Experiment (ESTOFEX) forecasts. Atmospheric Research, 100, 538-546.

Three years of forecasts of lightning and severe thunderstorms from the European Storm Forecast Experiment (ESTOFEX) have been evaluated. The forecasts exhibit higher quality in summer than in winter and there is some evidence that they have improved over the course of the evaluation. Five individual forecasters made the majority of the forecasts and differences in their forecasts are on the order of the overall variability of the forecast quality. As a result, the forecasts appear to come from a single unit, rather than from a group of individuals.
The graphical description of the probability of detection and frequency of hits recently developed by Roebber is a valuable tool for displaying the time series of lightning forecast performance. It also appears that, even though they are not intended for that purpose, using the lightning forecasts as a low-end forecast of severe thunderstorms is potentially useful for decision makers.

Available online at http://www.nssl.noaa.gov/users/brooks/public_html/papers/brooksetalestofex2011.pdf.

Brotzge, J., S. Erickson, H. Brooks, 2011: A five-year climatology of tornado false alarms. Weather and Forecasting, 26, 534-544.

During 2008 approximately 75% of tornado warnings issued by the National Weather Service (NWS) were false alarms. This study investigates some of the climatological trends in the issuance of false alarms and highlights several factors that impact false alarm ratio (FAR) statistics. All tornadoes and tornado warnings issued across the continental U.S. between 2000 and 2004 were analyzed, and the data were sorted by hour of the day, month of the year, geographical region and weather forecast office (WFO), the number of tornadoes observed on a day in which a false alarm was issued, distance of the warned area from the nearest NWS radar, county population density and county area.

Analysis of the tornado false alarm data identified six specific trends. First, the FAR was highest during non-peak storm periods, such as during the night and during the winter and late summer. Second, the FAR was strongly tied to the number of tornadoes warned per day. Nearly one-third of all false alarms were issued on days when no tornadoes were confirmed within the WFO’s county warning area. Third, the FAR varied with distance from radar, with significantly low estimates found beyond 150 km from radar. Fourth, the FAR varied with population density. For warnings within 50 km of a NWS radar, FAR increased with population density; however, for warnings beyond 150 km from radar, FAR decreased regardless of population density. Fifth, the FAR also varied as a function of county size. The FAR was generally highest for the smallest counties; the FAR was ~80% for all counties < 1000 km2 regardless of distance from radar. Finally, the combined effects of distance from radar, population density, and county size led to significant variability across geographic regions.

Bukovsky, M. S., J. S. Kain, M. E. Baldwin, 2006: Bowing Convective Systems in a Popular Operational Model: Are They for Real?. Weather and Forecasting, 21, 307-324.

Bowing, propagating precipitation features that sometimes appear in NCEP's North American Mesoscale model (NAM; formerly called the Eta Model) forecasts are examined. These features are shown to be associated with an unusual convective heating profile generated by the Betts–Miller–Janji convective parameterization in certain environments. A key component of this profile is a deep layer of cooling in the lower to middle troposphere. This strong cooling tendency induces circulations that favor expansion of parameterized convective activity into nearby grid columns, which can lead to growing, self-perpetuating mesoscale systems under certain conditions. The propagation characteristics of these systems are examined and three contributing mechanisms of propagation are identified. These include a mesoscale downdraft induced by the deep lower-to-middle tropospheric cooling, a convectively induced buoyancy bore, and a boundary layer cold pool that is indirectly produced by the convective scheme in this environment. Each of these mechanisms destabilizes the adjacent atmosphere and decreases convective inhibition in nearby grid columns, promoting new convective development, expansion, and propagation of the larger system. These systems appear to show a poor correspondence with observations of bow echoes on time and space scales that are relevant for regional weather prediction, but they may provide important clues about the propagation mechanisms of real convective systems.

Case, J. L., S. R. Dembek, J. S. Kain, S. V. Kumar, T. Matsui, J. J. Shi, W. M. LaPenta, W. K. Tao, 2008: A sensitivity study of the operational NSSL WRF using unique NASA assets. Preprints, 9th Annual WRF Users' Workshop, Boulder, CO, USA, NCAR, P9.4.

Available online at http://www.mmm.ucar.edu/wrf/users/workshops/WS2008/abstracts/P9-04.pdf.

Clark, A. J., J. S. Kain, D. J. Stensrud, M. Xue, F. Kong, M. C. Coniglio, K. W. Thomas, Y. Wang, K. Brewster, J. Gao, X. Wang, S. J. Weiss, J. Du, 2011: Probabilistic precipitation forecast skill as a function of ensemble size and spatial scale in a convection-allowing ensemble. Monthly Weather Review, 139, 1410-1418.

Available online at http://journals.ametsoc.org/doi/pdf/10.1175/2010MWR3624.1.

Clark, A. J., S. J. Weiss, J. S. Kain, I. L. Jirak, M. C. Coniglio, C. J. Melick, C. Siewert, R. A. Sobash, P. T. Marsh, A. R. Dean, M. Xue, F. Kong, K. W. Thomas, Y. Wang, K. Brewster, J. Gao, X. Wang, J. Du, D. R. Novak, F. E. Barthold, M. J. Bodner, J. J. Levit, C. B. Entwistle, T. L. Jensen, J. C. Correia, 2012: An Overview of the 2010 Hazardous Weather Testbed Experimental Forecast Program Spring Experiment. Bulletin of the American Meteorological Society, 139, 55-74.

The NOAA Hazardous Weather Testbed (HWT) conducts annual spring forecasting experiments organized by the Storm Prediction Center and National Severe Storms Laboratory to test and evaluate emerging scientific concepts and technologies for improved analysis and prediction of hazardous mesoscale weather. A primary goal is to accelerate the transfer of promising new scientific concepts and tools from research to operations through the use of intensive real-time experimental forecasting and evaluation activities conducted during the spring and early summer convective storm period. The 2010 NOAA/HWT Spring Forecasting Experiment (SE2010), conducted 17 May through 18 June, had a broad focus, with emphases on heavy rainfall and aviation weather, through collaboration with the Hydrometeorological Prediction Center (HPC) and the Aviation Weather Center (AWC), respectively. In addition, using the computing resources of the National Institute for Computational Sciences at the University of Tennessee, the Center for Analysis and Prediction of Storms at the University of Oklahoma provided unprecedented real-time conterminous United States (CONUS) forecasts from a multimodel Storm-Scale Ensemble Forecast (SSEF) system with 4-km grid spacing and 26 members and from a 1-km grid spacing configuration of the Weather Research and Forecasting model. Several other organizations provided additional experimental high-resolution model output. This article summarizes the activities, insights, and preliminary findings from SE2010, emphasizing the use of the SSEF system and the successful collaboration with the HPC and AWC.

Cohen, A. E., M. C. Coniglio, S. F. Corfidi, S. J. Corfidi, 2006: Discrimination among non-severe, severe, and derecho-producing mesoscale convective system environments. Extended Abstracts, Severe Local Storms Symposium, 86th Amer. Meteor. Soc. Annual Meeting, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P1.15. [Available from National Weather Center, 120 David L. Boren Blvd, Norman, OK, USA, 73071.]

Available online at http://ams.confex.com/ams/pdfpapers/103614.pdf.

Cohen, A. E., M. C. Coniglio, S. F. Corfidi, S. J. Corfidi, 2007: Discrimination of Mesoscale Convective System Environments Using Sounding Observations. Weather and Forecasting, 22, 1045-1062.

Coniglio, M. C., D. J. Stensrud, L. J. Wicker, 2006: Effects of upper-level shear on the structure and maintenance of strong quasi-linear mesoscale convective systems. Journal of the Atmospheric Sciences, 63, 1231-1252.

Recent observational studies have shown that strong midlatitude mesoscale convective systems (MCSs) tend to decay as they move into environments with less instability and smaller deep-layer vertical wind shear. These observed shear profiles that contain significant upper-level shear are often different from the shear profiles considered to be the most favorable for the maintenance of strong, long-lived convective systems in some past idealized simulations. Thus, to explore the role of upper-level shear in strong MCS environments, a set of two-dimensional (2D) simulations of density currents within a dry, statically neutral environment is used to quantify the dependence of lifting along an idealized cold pool on the upper-level shear. A set of three-dimensional (3D) simulations of MCSs is produced to gauge the effects of the upper-level shear in a more realistic framework.

Results from the 2D experiments show that the addition of upper-level shear to a wind profile with weak to moderate low-level shear increases the vertical displacement of parcels despite a decrease in the vertical velocity along the cold pool interface. Parcels that are elevated above the surface (1–2 km) overturn and are responsible for the deep lifting in the deep-shear environments, while the surface-based parcels typically are lifted through the cold pool region in a rearward-sloping path. This deep overturning helps to maintain the leading convection and greatly increases the size and total precipitation output of the convective systems in more complex 3D simulations, even in the presence of 3D structures. These results show that the shear profile throughout the entire troposphere must be considered to gain a more complete understanding of the structure and maintenance of strong midlatitude MCSs.

Coniglio, M. C., S. F. Corfidi, 2006: Forecasting the speed and maintenance of severe mesoscale convective systems. Extended Abstracts, Severe Local Storms Symposium at the 86th AMS annual meeting, Atlanta, GA, USA, American Meteorological Society, CD-ROM, P1.30. [Available from National Weather Center, 120 David L. Boren Blvd, Norman, OK, USA, 73071.]

Available online at http://ams.confex.com/ams/pdfpapers/104815.pdf.

Coniglio, M. C., H. E. Brooks, S. F. Corfidi, S. J. Weiss, 2007: Forecasting the Maintenance of Quasi-Linear Mesoscale Convective Systems. Weather and Forecasting, 22, 556-570.

The problem of forecasting the maintenance of mesoscale convective systems (MCSs) is investigated through an examination of observed proximity soundings. Furthermore, environmental variables that are statistically different between mature and weakening MCSs are input into a logistic regression procedure to develop probabilistic guidance on MCS maintenance, focusing on warm-season quasi-linear systems that persist for several hours.
Between the mature and weakening MCSs, shear vector magnitudes over very deep layers are the best discriminators among hundreds of kinematic and thermodynamic variables. An analysis of the shear profiles reveals that the shear component perpendicular to MCS motion (usually parallel to the leading line) accounts for much of this difference in low levels and the shear component parallel to MCS motion accounts for much of this difference in mid-to-upper levels. The lapse rates over a significant portion of the convective cloud layer, the convective available potential energy, and the deep-layer mean wind speed are also very good discriminators and collectively provide a high level of discrimination between the mature and dissipation soundings as revealed by linear discriminant analysis. Probabilistic equations developed from these variables used with short-term numerical model output show utility in forecasting the transition of an MCS with a solid line of 50+ dbZ echoes to a more disorganized system with unsteady changes in structure and propagation. This study shows that empirical forecast tools based on environmental relationships still have the potential to provide forecasters with improved information on the qualitative characteristics of MCS structure and longevity. This is especially important since the current and near-term value added by explicit numerical forecasts of convection is still uncertain.

Coniglio, M. C., D. C. Dowell, L. J. Wicker, 2007: Ensemble Kalman filter assimilation of Doppler radar data: Analyses of a developing MCS. Extended Abstracts, 22nd Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, American Meteorlogical Society, 3B.3. [Available from Michael Coniglio, NSSL/FRDD, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Recent efforts at the National Severe Storms Laboratory and the University of Oklahoma/Center for Analysis and Prediction of Storms have shown the positive impact of assimilating real Doppler velocity and reflectivity observations using an Ensemble Kalman Filter (EnKF) technique for the storm-scale analysis of supercell thunderstorms. Recently, the utility of this technique to other convective modes with multiple updrafts and more complex evolutions has been shown with analyses of the 16-17 June 2005 severe bow echo MCS across Oklahoma. It is well known that an accurate depiction of convective system cold pools is a prerequisite for the accurate short-term (1-12 h) prediction of MCSs by high-resolution numerical models. One of the most promising aspects of the analysis is the detailed and accurate depiction of the cold convective outflow and the robustness of the analyses to changes in the experimental design (although the well-known sensitivity to microphysics is still apparent). This talk will highlight the successful analysis of this event and discuss the mechanics of the EnKF procedure applied to a real and complex convective situation. In addition, the relative merits of 1-h forecasts produced from the EnKF analyses and the many outstanding issues that need to be addressed before these techniques can be applied in real time will be discussed.

Available online at http://ams.confex.com/ams/pdfpapers/124285.pdf.

Coniglio, M. C., J. S. Kain, S. J. Weiss, M. Xue, M. L. Weisman, Z. I. Janjic, 2007: Evaluating storm-scale model output for severe-weather forecasting: The 2007 NOAA HWT Spring Experiment.. Preprints, 4th European Conference on Severe Storms, Trieste, Italy, International Centre for Theoretical Physics, CD-ROM, 03.11.

Coniglio, M. C., A. E. Cohen, S. F. Corfidi, S. J. Corfidi, 2007: Discrimination of MCS environments using sounding observations. Weather and Forecasting, 22, 1045-1062.

The prediction of the strength of mesoscale convective systems (MCSs) is a major concern to operational meteorologists and the public. To address this forecast problem, this study examines meteorological variables derived from sounding observations taken in the environment of quasi-linear MCSs. A set of 186 soundings that sampled the beginning and mature stages of the MCSs are categorized by their production of severe surface winds into weak, severe, and derecho-producing MCSs. Differences in the variables among these three MCS categories are identified and discussed. Mean low- to upper-level wind speeds and deep-layer vertical wind shear, especially the component perpendicular to the convective line, are excellent discriminators among all three categories. Low-level inflow relative to the system is found to be an excellent discriminator, largely because of the strong relationship of system severity to system speed. Examination of the mean wind and shear vectors relative to MCS motion suggests that cell propagation along the direction of cell advection is a trait that separates severe, long-lived MCSs from the slower-moving, nonsevere variety and that this is favored when both the deep-layer shear vector and the mean deep-layer wind are large and nearly parallel. Midlevel environmental lapse rates are found to be very good discriminators among all three MCS categories, while vertical differences in equivalent potential temperature and CAPE only discriminate well between weak and severe/derecho MCS environments. Knowledge of these variables and their distribution among the different categories of MCS intensity can be used to improve forecasts and convective watches for organized convective wind events.

Coniglio, M. C., J. S. Kain, S. J. Weiss, D. R. Bright, J. J. Levit, M. Xue, M. L. Weisman, Z. I. Janjic, M. Pyle, J. Du, D. J. Stensrud, 2007: Evaluating WRF model output for severe-weather forecasting: The 2007 NOAA HWT Spring Experiment.. Extended Abstracts, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, American Meteorological Society, CD-ROM, 11A.2.

Coniglio, M. C., M. Bardon, K. Virts, S. J. Weiss, 2006: Forecasting the maintenance of mesoscale convective systems.. Extended Abstracts, 23rd Conf. on Severe Local Storms, St. Louis, MO, USA, American Meteorological Society, CD-ROM, 2.3.

Coniglio, M. C., J. S. Kain, S. J. Weiss, D. R. Bright, J. J. Levit, G. W. Carbin, K. W. Thomas, F. Kong, M. Xue, M. L. Weisman, M. E. Pyle, K. L. Elmore, 2008: Evaluation of WRF model output for severe-weather forecasting from the 2008 NOAA Hazardous Weather Testbed Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.4. [Available from Michael C. Coniglio, NSSL, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142060.htm.

Coniglio, M. C., K. L. Elmore, J. S. Kain, S. J. Weiss, M. Xue, M. L. Weisman, 2010: Evaluation of WRF model output for severe weather forecasting from the 2008 NOAA Hazardous Weather Testbed Spring Experiment. Weather and Forecasting, 25, 408-427.

This study assesses forecasts of the preconvective and near-storm environments from the convectionallowing
models run for the 2008 National Oceanic and Atmospheric Administration (NOAA) Hazardous
Weather Testbed (HWT) spring experiment. Evaluating the performance of convection-allowing models
(CAMs) is important for encouraging their appropriate use and development for both research and operations.
Systematic errors in theCAMforecasts included a cold bias in mean 2-m and 850-hPa temperatures over most
of the United States and smaller than observed vertical wind shear and 850-hPa moisture over the high plains.
The placement of airmass boundaries was similar in forecasts from the CAMs and the operational North
American Mesoscale (NAM) model that provided the initial and boundary conditions. This correspondence
contributed to similar characteristics for spatial and temporalmean error patterns. However, substantial errors
were found in the CAM forecasts away from airmass boundaries. The result is that the deterministic CAMs
do not predict the environment as well as the NAM. It is suggested that parameterized processes used at
convection-allowing grid lengths, particularly in the boundary layer, may be contributing to these errors.
It is also shown that mean forecasts from an ensemble of CAMs were substantially more accurate than
forecasts from deterministic CAMs. If the improvement seen in the CAM forecasts when going from a deterministic
framework to an ensemble framework is comparable to improvements in mesoscale model forecasts
when going from a deterministic to an ensemble framework, then an ensemble of mesoscale model
forecasts could predict the environment even better than an ensemble of CAMs. Therefore, it is suggested that
the combination of mesoscale (convection parameterizing) andCAMconfigurations is an appropriate avenue
to explore for optimizing the use of limited computer resources for severe weather forecasting applications.

Coniglio, M. C., J. Y. Hwang, D. J. Stensrud, 2010: Environmental Factors in the Upscale Growth and Longevity of MCSs Derived from Rapid Update Cycle Analyses. Monthly Weather Review, 138, 3514-3539.

Composite environments of mesoscale convective systems (MCSs) are produced from Rapid Update Cycle (RUC) analyses to explore the differences between rapidly- and slowly-developing MCSs as well as the differences ahead of long-lived and short-lived MCSs. The composite analyses capture the synoptic-scale features known to be associated with MCSs and depict the inertial oscillation of the nocturnal low-level jet (LLJ), which remains strong but tends to veer away from decaying MCSs. The composite first-storms environment for the rapidly-developing MCSs contains a stronger LLJ located closer to the first storms region, much more conditional instability, potential instability, and energy available for downdrafts, smaller 3 – 10 km vertical wind shear, and smaller geostrophic potential vorticity in the upper troposphere, when compared to the environment for the slowly-developing MCSs. The weaker shear above 3 km for the rapidly-developing MCSs is consistent with supercell or discrete cell modes being less likely in weaker deep layer shear and the greater potential for a cold pool to trigger convection when the shear is confined to lower levels. Furthermore, these results suggest that low values of upper-level potential vorticity may signal a rapid transition to an MCS. The composite environment ahead of the genesis of long-lived MCSs contains a broader LLJ, a better-defined frontal zone, stronger low-level frontogenesis, deeper moisture and stronger wind shear above 2 km, when compared to short-lived MCSs. The larger shear above 2 km for the long-lived MCSs is consistent with the importance of shear elevated above the ground to help organize and maintain convection that feeds on the elevated unstable parcels after dark and is indicative of the enhanced baroclinicity ahead of the MCSs.

Coniglio, M. C., S. F. Corfidi, J. S. Kain, 2011: Environment and Early Evolution of the 8 May 2009 Derecho-Producing Convective System. Monthly Weather Review, 139, 1083-1102.

This study documents the complex environment and early evolution of the remarkable derecho that traversed portions of the central United States on 8 May 2009. Central to this study is the comparison of the 8 May 2009 derecho environment to that of other mesoscale convective systems (MCSs) that occurred in the central United States during a similar time of year. Synoptic-scale forcing was weak and thermodynamic instability was limited during the development of the initial convection, but several mesoscale features of the environment appeared to contribute to initiation and upscale growth, including a mountain wave, a midlevel jet streak, a weak midlevel vorticity maximum, a “Denver cyclone,” and a region of upper-tropospheric inertial instability.

The subsequent MCS developed in an environment with an unusually strong and deep low-level jet (LLJ), which transported exceptionally high amounts of low-level moisture northward very rapidly, destabilized the lower troposphere, and enhanced frontogenetical circulations that appeared to aid convective development. The thermodynamic environment ahead of the developing MCS contained unusually high precipitable water (PW) and very large midtropospheric lapse rates, compared to other central plains MCSs. Values of downdraft convective available potential energy (DCAPE), mean winds, and 0–6-km vertical wind shear were not as anomalously large as the PW, lapse rates, and LLJ. In fact, the DCAPE values were lower than the mean values in the comparison dataset. These results suggest that the factors contributing to updraft strength over a relatively confined area played a significant role in generating the strong outflow winds at the surface, by providing a large volume of hydrometeors to drive the downdrafts.

Coniglio, M. C., J. Y. Hwang, D. J. Stensrud, 2011: CORRIGENDUM. Monthly Weather Review, 139, 2686-2688.

Coniglio, M. C., S. F. Corfidi, J. S. Kain, 2012: Views on Applying RKW Theory: An Illustration Using the 8 May 2009 Derecho-Producing Convective System. Monthly Weather Review, 140, 1023-1043.

This work presents an analysis of the vertical wind shear during the early stages of the remarkable 8 May 2009 central U.S. derecho-producing convective system. Comments on applying Rotunno–Klemp–Weisman (RKW) theory to mesoscale convective systems (MCSs) of this type also are provided. During the formative stages of the MCS, the near-surface-based shear vectors ahead of the leading convective line varied with time, location, and depth, but the line-normal component of the shear in any layer below 3 km ahead of where the strong bow echo developed was relatively small (6–9 m s−1). Concurrently, the midlevel (3–6 km) line-normal shear component had magnitudes mostly >10 m s−1 throughout.

In a previous companion paper, it was hypothesized that an unusually strong and expansive low-level jet led to dramatic changes in instability, shear, and forced ascent over mesoscale areas. These mesoscale effects may have overwhelmed the interactions between the cold pool and low-level shear that modulate system structure in less complex environments. If cold pool–shear interactions were critical to producing such a strong system, then the extension of the line-normal shear above 3 km also appeared to be critical. It is suggested that RKW theory be applied with much caution, and that examining the shear above 3 km is important, if one wishes to explain the formation and maintenance of intense long-lived convective systems, particularly complex nocturnal systems like the one that occurred on 8 May 2009.

Corfidi, S. F., S. J. Weiss, J. S. Kain, S. J. Corfidi, R. M. Rabin, J. L. Levit, 2010: Revisiting the 3-4 April 1974 super outbreak of tornadoes. Weather and Forecasting, 25, .

The Super Outbreak of tornadoes over the central and eastern United States on 3–4 April 1974 remains the most outstanding severe convective weather episode on record in the continental United States. The outbreak far surpassed previous and succeeding events in severity, longevity, and extent. In this paper, surface, upper-air, radar, and satellite data are used to provide an updated synoptic and subsynoptic overview of the event. Emphasis is placed on identifying the major factors that contributed to the development of the three main convective bands associated with the outbreak, and on identifying the conditions that may have contributed to the outstanding number of intense and long-lasting tornadoes. Selected output from a 29-km, 50-layer version of the Eta forecast model, a version similar to that available operationally in the mid-1990s, also is presented to help depict the evolution of thermodynamic stability during the event.

Diffenbaugh, N. S., R. J. Trapp, H. E. Brooks, 2008: Does Global Warming Influence Tornado Activity?. EOS, TRANSACTIONS, AMERICAN GEOPHYSICAL UNION, 89, 533-534.

Tornadoes and other severe thunderstorm phenomena frequently cause as much annual property damage in the United States as do hurricanes, and often cause more fatalities (see http://www.nws.noaa.gov/om/hazstats.shtml). In 2008, there were 2176 preliminary tornado reports logged through mid-December, with 1600 “actual counts” (duplicate reports removed) through September, the highest total in the past half century (Figure 1). The mass media have covered these events extensively, and experts have been deluged with requests for explanations, including possible links to anthropogenic global warming. Although recent research has yielded insight into the connections between global warming and tornado and severe thunderstorm forcing, these relationships remain mostly unexplored, largely because of the challenges in observing and numerically simulating tornadoes. Indeed, a number of questions that have been answered for other climate-related phenomena remain particularly difficult for climate and severe weather scientists, including whether there are detectable trends in tornado occurrence and if so, what causes them. This article explores the challenges and opportunities in pursuing these areas of research.

Available online at http://www.agu.org/journals/eo/eo0853/2008EO530001.pdf.

Doswell III, C. A., H. E. Brooks, N. Dotzek, 2009: On the implementation of the enhanced Fujita scale in the USA. Atmospheric Research, 93, 554-563.

The history of tornado intensity rating in the United States of America (USA), pioneered by T. Fujita, is reviewed, showing that non-meteorological changes in the climatology of the tornado intensity ratings are likely, raising questions about the temporal (and spatial) consistency of the ratings. Although the Fujita scale (F-scale) originally was formulated as a peak wind speed scale for tornadoes, it necessarily has been implemented using damage to estimate the wind speed. Complexities of the damage-wind speed relationship are discussed.

Recently, the Fujita scale has been replaced in the USA as the official system for rating tornado intensity by the so-called Enhanced Fujita scale (EF-scale). Several features of the new rating system are reviewed and discussed in the context of a proposed set of desirable features of a tornado intensity rating system.

It is concluded that adoption of the EF-scale in the USA may have been premature, especially if it is to serve as a model for how to rate tornado intensity outside of the USA. This is in large part because its degree of damage measures used for estimating wind speeds are based on USA-specific construction practices. It is also concluded that the USA's tornado intensity rating system has been compromised by secular changes in how the F-scale has been applied, most recently by the adoption of the EF-scale. Several recommendations are offered as possible ways to help develop an improved rating system that will be applicable worldwide.

Doswell III, C. A., G. W. Carbin, H. E. Brooks, 2012: The tornadoes of spring 2011 in the USA: an historical perspective. Weather, 67, 88-94.

No abstract

Douglas, M. W., J. Mejia, J. Murillo, R. Orozco, 2007: Spatial Structure of Cloudiness Associated with the Mid-Summer Drought from MODIS and GOES Imagery. Extended Abstracts, AGU Joint Assembly, Acapulco, Mexico, AGU, H51G-04.

Douglas, M. W., R. Orozco, J. F. Mejia, 2008: Mapping the spatial extent of the Central American mid-summer drought with MODIS and GOES imagery. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, American Meteorological Society, P1C.10. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Many parts of Central America and southern Mexico experience an extended dry period within the longer period of summer rains. This mid-summer drought (MSD), usually during July and August, shows a complicated spatial structure, reflecting the interaction of the large-scale synoptic flow and the varied topography of the region. We have used MODIS imagery (250 m resolution) and GOES 10 km imagery for the years 1983 to 2006 to describe the spatial structure of the cloudiness associated with the MSD. Compositing results using specific periods and also by using different indices (trade wind intensity and cloudiness over specific domains) will be shown. The importance (and challenge) of identifying suitable indices that represent the MSD will be discussed.

Douglas, M. W., J. F. Mejia, 2008: Aircraft measurements of temperature anomalies associated with tropical waves during NAMMA. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, American Meteorological Society, P1E.4. [Available from Michael W Douglas, 120, Norman, OK, USA, 73072.]

Special measurements were made of tropical waves over the far eastern tropical Atlantic during the NASA-AMMA field program during August and September 2006. One objective of this program was to help determine why some waves develop rapidly into tropical storms while most do not. This presentation shows the temperature anomalies associated with the different waves sampled by the dropsonde and flight level data from the NASA DC-8 and also other estimates of the temperature field from in-situ soundings. The analyses will be compared both with operational global analyses and with mesoscale analyses produced by assimilating the aircraft observations with the WRF model.

Douglas, M. W., J. F. Mejia, R. Orozco, S. Henry, 2008: Quantifying the extent and degree of cloud-affected tropical environments with MODIS imagery. Two extreme environments: Lomas and cloud forests. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, American Meteorological Society, 10.1. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Quantifying the extent and degree of cloud-affected tropical environments with MODIS imagery. Two extreme environments: Lomas and cloud forests

Michael W. Douglas, NOAA/NSSL, Norman, OK; and J. F. Mejia, R. Orozco, and S. Henry

Using a simple algorithm for extracting cloudiness from the visible MODIS imagery we have developed short-period (~ several years) cloudiness climatologies for different tropical regions at 250m spatial resolution. This presentation focuses on two environments that are difficult to accurately delineate with conventional climate data or even current satellite-based rainfall estimation techniques. One such environment, tropical cloud forest, is characterized by very high precipitation and also high cloudiness. However, cloud forest is mostly distinguished from surrounding lowland rain forest by the very high frequency of cloudiness and its small spatial extent. The second environment of our study is the coastal fog/low cloud zone along arid coastlines (known as “lomas” in Peru). These regions receive almost no rainfall, yet have vegetation supported by the frequent low clouds that intercept the topography along the coast. Such areas are even more difficult to identify from raingauges or satellite rainfall estimates than cloud forests.

We have developed a simple algorithm to use the cloudiness frequencies obtained from the MODIS imagery to classify the “intensity” of both the cloud forests and the lomas. The algorithm uses MODIS imagery from the NASA Terra and Aqua satellites to stratify cloudiness by annual amount, seasonality, and diurnal variability. Areas most favorable for vegetation growth are those with maximum annual frequency of cloudiness and minimum seasonality and diurnal variation, other factors being equal.S

Douglas, M. W., J. F. Mejia, J. F. Galvez, J. Murillo, R. Orozco, 2008: West African pilot balloon network during the NAMMA-2006 and implications for the future of the African pilot balloon sounding network.. Preprints, The 88th Annual Meeting (20-24 January 2008) (New Orleans, LA), New Orleans, LA, USA, American Meteorological Society, 15B.5. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

The West African pilot balloon network during the NAMMA-2006 and implications for the future of the African pilot balloon sounding network

Michael W. Douglas, NOAA/NSSL, Norman, OK; and J. Murillo, J. F. Mejia, J. M. Galvez, and R. Orozco

The pilot balloon network in West Africa has been in place for more than 50 years, and in the past the network was characterized by relatively frequent observations (often 4-times daily) and with high spatial density (more than 20 stations in West Africa). Such a network would be potentially very useful in helping to track the African waves that typically evolve into tropical storms over the Atlantic Ocean. However, the pilot balloon network has decayed in recent decades. The NAMMA (NASA-African Monsoon Multidisciplinary Analysis (AMMA)), involving a field campaign in 2006, afforded an opportunity to attempt to re-invigorate the pilot balloon network. One component of NAMMA involved strengthening the pilot balloon wind sounding network over west Africa to help describe the intensity of African waves exiting the continent. Four countries were the focus of this work and 10 stations were visited over the course of one month just prior to the NAMMA. Many technical problems were encountered and dealt with, but many problems were related to the personnel and the organization of the National Meteorological Services of the region. Some success was achieved in making the observations, but considerably less than was initially expected. This talk summarizes the main problems encountered, our short-term solutions, and our perspectives on how renovating this potentially-valuable network may be possible.

Douglas, M. W., J. M. Murillo, R. K. Orozco, J. F. Mejias, 2008: Underutilized observations for studying tropical climate variations: the historical pilot balloon database.. Preprints, The 88th Annual Meeting (20-24 January 2008) (New Orleans, LA), New Orleans, LA, USA, American Meteorological Organization, 3B.6. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Underutilized observations for studying tropical climate variations: the historical pilot balloon data base

Michael W. Douglas, NOAA/NSSL, Norman, OK; and R. Orozco, J. F. Mejia, and J. Murillo

The longest-running atmospheric sounding data base is that from pilot balloon observations (“pibals”), whose routine observations date from the early 20th century. Such observations are still made today, though mostly in developing countries in Asia and Africa. Although pibals are subject to limitations (cloudiness and darkness being the two most obvious ones), their low cost has historically allowed for more frequent and more widespread use than radiosondes. Much less well-known, and less appreciated, is that pibals have some advantages over radiosonde winds for studies of climate variability. The procedure for making a pibal has not fundamentally changed in 100 years, unlike wind observations obtained from rawinsonde systems – which have used radiotheodolites, Omega, LORAN and now GPS. Wind profiles obtained from these different systems show somewhat differing characteristics, which can complicate identifying historical trends in wind data.

Making effective use of historical pilot balloon data for climate studies requires availability of the original angle data and some metadata - such as the characteristics of the balloons and inflation procedures. We discuss the difficulty in obtaining both of these; a major effort at digitizing the global data base of pilot balloon observations will be required. Studies are underway (results will be shown) to evaluate the uncertainties introduced into mean wind profiles due to missing data (generally due to clouds), and the observational errors that characterize different pibal networks. These need to be known to determine the limitations of pibals for describing and monitoring regional climate variations.

Douglas, M. W., J. Murillo, J. F. Mejia, 2008: Two courses missing from meteorology programs at US universities.. Preprints, The 88th Annual Meeting (20-24 January 2008) (New Orleans, LA), New Orleans, LA, USA, American Meteorological Society, P1.35. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Two courses missing from US university meteorology programs

Michael W. Douglas, NOAA/NSSL, Norman, OK; and J. Murillo and J. F. Mejia

This presentation describes the need for, and potential content of, two meteorological courses usually lacking in meteorology programs at US universities. These subjects are somewhat related and potentially could be combined into one course. The first subject is that of “Design and execution of field programs in the atmospheric sciences”. While it might be argued that there is such diversity in meteorological field activities that “hands-on” learning is best, there are many aspects common to most field studies that students could benefit from via formal lectures. Such a course might best be taught at the advanced graduate level, where students are closer to participating in, and perhaps helping design, such activities. The second, somewhat complementary course, might be titled “International Meteorological Activities and the functions of National Meteorological Services”. Rarely are US students (unlike foreign students) exposed to the enormous variety of meteorological activities that occur globally. An equally small number of students have a good conceptual understanding of the different components of any National Meteorological Service (including that of the US). Material common to both courses would include covering the existing (and research) observing systems across the globe – this material is often left out of courses on meteorological instrumentation.

Motivation for developing this material has come from the development of courses for international audiences with widely varying backgrounds. A sample syllabus will be provided to stimulate discussion.

Douglas, M. W., J. Murillo, R. Orozco, J. M. Galvez, J. F. Mejia, 2006: Accuracy of the Aviation Model (AVN) final analyses over Central South America based upon upper air observations collected during the SALLJEX.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, AMS, PC1-24.

Douglas, M. W., J. M. Galvez, C. R. Reyes, R. Orozco, 2006: Observed diurnal circulations and rainfall over the altiplano during the SALLJEX.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PA1-9.

Douglas, M. W., J. M. Galvez, 2006: Modulation of rainfall by Lake Titicaca using the WRF Model.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PB1-21.

Douglas, M. W., J. M. Galvez, 2006: Northward-propagating surges east of the Andes during the SALLJEX.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PB3-33.

Douglas, M. W., J. F. Mejia, 2006: Flow around the Andean elbow from WRF simulations and P-3 aircraft measurements during SALLJEX.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PB3-32.

Douglas, M. W., J. M. Galvez, R. Orozco, J. F. Mejjia, 2006: Plausible effects of Paleolake Tauca on the altiplano circulations and rainfall from WRF model simulations.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PB3-34.

Douglas, M. W., J. Regalado, J. Murillo, 2006: Atmospheric soundings across an oceanic front between the Galapagos Islands and the coast of South America from the INOCAR cruise of October 2005.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PA3-33. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Special radiosonde observations were made from the INOCAR research vessel Orion during the
second INOCAR oceanographic cruise of 2005. These observations were carried out for both
operational and scientific objectives. Operationally, we sought to evaluate the feasibility of
routinely making radiosonde observations from the ship, and determining what the ship might
need for such observations. Since relatively few upper air observations have been made
between the Galapagos Islands and the coast of Ecuador we wanted to obtain high spatial
resolution soundings across the equatorial cold tongue, which has been the subject of recent
research measurements farther west in the eastern Pacific. Some results of the boundary layer
over the cold tongue, based on the radiosonde measurements, are reported here. With some
modifications, the Orion is a suitable platform for routine atmospheric measurements in this
poorly sampled region of the eastern Pacific.

Douglas, M. W., L. Florez, N. Ordinola, J. Murillo, 2006: Variability of the meridional flow near the Equator from 8 years of pilot balloon observations at Piura, Peru.. Preprints, 8th International Conference on Southern Hemisphere Meteorology and Oceanography (ICSHMO), Foz do Iguazu, Brazil, American Meteorological Society, PD3-14. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, Brazil, 73072.]

Pilot balloon observations have been made at Piura, Peru since 1997 as part of the PACS–SONET project. This data set is the most complete set of observations from SONET, andillustrates the value of a single station’s multi-year record for studies of interannual variability ofthe windfield near the equator.

Douglas, M. W., R. Orozco, J. M. Galvez, J. Murillo, J. F. Mejia, 2006: The seasonal evolution of the diurnal variation of the low-level winds around the Gulf of California. Is there a link to vegetation green-up during the wet season?. Preprints, 86th American Meteorological Annual Meeting (18th Conference on Climate Variability and Change), Atlanta, GA, Atlanta, GA, USA, American Meteorological Society, J3.4. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

Sea-land breeze circulations are ubiquitous along the Gulf of California. Sea breezes are well developed because of the strong heating over the desertic regions along both sides of the Gulf. However, the sea surface temperature has a large seasonal range, especially over the northern Gulf. In addition, after the start of the summer rains there is a rapid foliation of the seasonal dry forest found along the eastern side of the Gulf. It was hypothesized that the rapid vegetation change and associated change in the land surface characteristics (albedo and evapotranspiration) might modify the sea-land breeze circulations. This might in turn affect the diurnal evolution of rainfall over the region. The recently ended North American Monsoon Experiment (NAME) afforded an opportunity to determine the possible seasonal variation of the sea-breeze intensity and its relationship with the onset of the rainy season. This presentation will describe the effort to measure the diurnal cycle of the winds and its seasonal variation. A network of 7 pilot balloon stations made observations twice-daily for approximately four months, with two of these making more frequent observations during special periods. Surface observations from automated surface stations were also available. The monthly mean winds from the different stations will be shown, as well as divergence estimates over different subregions of the pilot balloon array. The changes in sea-breeze intensity and the area-averaged divergence estimates will be compared with the seasonal evolution of the Gulf surface temperature and mean land surface temperature changes and the observed rainfall onset over the region.

Douglas, M. W., R. Orozco, J. M. Galvez, 2006: Diurnal variability of the cloud field over the VOCALS domain from GOES imagery.. Preprints, 86th American Meteorological Annual Meeting (14th Conference on Interaction of the Sea and Atmosphere), Atlanta, GA, USA, American Meteorological Society, P1.3. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

As part of ongoing studies of mesoscale variability over the South American altiplano we have produced averages of the cloudiness using GOES imagery. These composites are made at full resolution of the imagery, to help identify the relationship between the underlying topography and the cloud field. The upcoming VOCALS activity, focused on the stratocumulus region of the southeastern Pacific, has as one objective the description of the diurnal cycle of this cloudiness and its relationship to the South American continent. With this in mind, we have produced GOES imagery composites for the SE Pacific with 30 min temporal resolution. These composites show the diurnal variation of the cloudiness and its apparent propagation offshore. The composites are stratified by time of year. Comparison is made with the simulated diurnal cycles reported in the literature.

Douglas, M. W., T. Killeen, J. F. Mejia, 2006: Use of MODIS and GOES imagery to help delineate the distribution of cloud forests along the eastern Andean slopes.. Preprints, (14th Conference on Satellite Meteorology and Oceanography), Atlanta, GA, USA, American Meteorological Society, P3.18. [Available from Michael W Douglas, 120 David Boren Boulevard, Norman, OK, USA, 73072.]

The environment with the greatest biodiversity from a global standpoint is that known as the tropical Andes “hotspot”, which is a broad region along the eastern slopes of the Andes in South America. One of the subregions with the highest diversity within this region is the cloud forest, a region of very high cloudiness and high annual precipitation. Mapping the cloud forest and surrounding environments has been of high priority because resources for conservation are limited and conservation organizations and governmental agencies need to know what areas should receive highest priority for protection efforts.

Work associated with the South American Low-level Jet Experiment (SALLJEX) carried out in 2002-3 led to the use of GOES imagery to develop composites of visible and IR imagery for describing the mean cloudiness along the eastern slopes of the Andes. More recently MODIS imagery has been used to describe cloudiness at even higher resolution. Together, these imagery sources provide clues as to the distribution of cloudiness that can be related to cloud forest environment. In addition, dry canyon environments, the locus of many geographically-restricted species, can likewise be readily described from the cloudiness composites.

The GOES and MODIS cloudiness composites will be shown, and some limitations of inferring cloud forest locations and dry canyon habitat from the imagery will be discussed. The potential for this technique to be applied to other areas will be mentioned.

Douglas, M. W., 2008: The Pan American Climate Studies Sounding Network. Bulletin of the American Meteorological Society, 89, 1709-1725.

A research effort primarily involving pilot balloon observations was carried out during the summer of 1997 to study rainfall variability over Central America. This activity, supported by NOAA's Pan American Climate Studies (PACS) program, grew in scope in response to the strong El Niño event of 1997/98 and subsequently evolved into a network ranging from Mexico to Paraguay. The overall goal of the PACS-Sounding Network (PACS-SONET) was to obtain relatively inexpensive wind profiles for describing climate variability over parts of the intertropical Americas that were not well covered by routine radiosonde observations. Major portions of the project supported climate research programs focusing on both the South and North American monsoon systems, while other parts of the network provided multiyear observations across important gaps in the Central American cordillera and also helped to describe cross-equatorial flow variations in the eastern Pacific. Approximately 50,000 observations were made by the PACS-SONET over its 10-yr operation.

This paper describes the motivation for and evolution of the network, the logistical complications that were involved in establishing and operating a long-term multinational network, and some of the important results from analysis of the data. We conclude by discussing some of our perspectives on why the network was unable to make a transition from research funding to one supported by meteorological services of the region.

Douglas, M. W., J. Mejia, R. Orozco, J. Murillo, 2008: Suggestions for upgrading the pilot balloon network in West Africa and elsewhere in the tropics. Extended Abstracts, TECO-2008 - WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation, St. Petersburg, Russian Federation, World Meteorological Organization, 1(9).

Based on experience during the 2006 NAMMA field program we provide some recommendations for improving the pilot balloon network over the West Africa region. These range from relatively straightforward suggestions as to adjusting the launch time to maximize sounding height, to improved efforts to maintain the equipment and train observers. The supply of gas for balloon inflation is probably the largest logistical problem, followed by quality control of the data. The paper concludes by suggesting that the fastest way to upgrade the sounding network over Africa is to make it independent of National Meteorological Services and place it under an independent body that would oversee all aspects of its operation – for the benefit of Numerical Weather Prediction and climate monitoring objectives. The reasons for this seemingly drastic action are presented.

Available online at http://www.knmi.nl/samenw/geoss/wmo/TECO2008/IOM-96-TECO2008/1(09)_Douglas_USA.pdf.

Douglas, M. W., 2008: Progress towards development of the glidersonde: a recoverable radiosonde system. Extended Abstracts, TECO-2008 - WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation, St. Petersburg, Russian Federation, World Meteorological Organization, P1(6).

The motivation and history of development of a recoverable radiosonde system using a glider lifted aloft by a radiosonde balloon – the “glidersonde”, is summarized in this poster. The current status of development efforts currently involve at least three separate groups; in the USA, in South Africa, and a version, developed in New Zealand, is now being marketed commercially. These efforts are briefly summarized, as are some limitations that still need to be overcome for widespread adoption of such technology.

Available online at http://www.knmi.nl/samenw/geoss/wmo/TECO2008/IOM-96-TECO2008/P1(06)_Douglas_USA.pdf.

Douglas, M. W., J. Mejia, N. Ordinola, J. Boustead, 2009: Synoptic Variability of Rainfall and Cloudiness along the Coasts of Northern Peru and Ecuador during the 1997/98 El Niño Event. Monthly Weather Review, 137, 116-136.

This paper describes the meteorological conditions associated with large fluctuations in rainfall over the coastal regions of northern Peru and Ecuador during the 1997/98 El Niño event. Using data from a network of routine rain gauges and special gauges established just prior to the onset of heavy rains, it is shown that large variations in the daily rainfall on quasi-weekly time scales occurred during the period January–April 1998. These rainfall fluctuations were approximately in phase along the coast from near the equator to ∼7°S. The daily rainfall data was averaged to develop a subset of wet and dry days, and then these dates were used as the basis for compositing. Special pilot balloon observations were composited with respect to the wet and dry days, showing that westerly and northerly wind anomalies are associated with wet spells. Composites of the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and outgoing longwave radiation (OLR) data support a modest association of anomalous westerly wind events with enhanced rainfall.

The relationship observed between westerly zonal wind anomalies and rainfall west of the Andes during 1998 suggested using the NCEP reanalysis to develop composites based on westerly wind events observed during other years. Zonal wind anomalies at 700 hPa were used as the primary criterion for stratifying “wet” and “dry” days, despite reservations about the association between rainfall and zonal wind. Compositing Geostationary Operational Environmental Satellite (GOES) and OLR data for 220 west wind anomaly events from the months of January–April for the years 1990–2005 showed that they are associated with enhanced cloudiness that propagates eastward at ∼10 m s−1. The composites using NCEP reanalyses show the evolution of the wind field associated with the wet days and suggest a link between extratropical wave passages across North America and anomalous westerly wind events off the coast of Ecuador and northern Peru.

Douglas, M. W., 2010: Adaptive sounding arrays for tropical regions. Extended Abstracts, 29th Conference on Hurricanes and Tropical Meteorology, Tucson, AZ, USA, American Meteorological Society, 12B.7.

The advent of low initial-cost radiosonde systems (relative to previous systems available on the market) permits the establishment of radiosonde networks that can be operated "on-demand". This talk will describe the essential requirements to affordably operate such sounding networks, with particular application to the region important for hurricanes affecting the US. Key to the effectiveness of such adaptive networks are 1) low initial cost of the sounding system which permits many sites to be established, 2) relatively infrequent need for observations, 3) availability of personnel that are paid by observation rather than full-time staff, and 4) suitable locations that exist for additional sounding sites to be established. Two-way communications with the stations is critical, since the observations would be intermittent. The greatest challenge is likely to be in deciding when to make observations – which observations are likely to have the greatest impact on forecast skill and over what time frame? A comparison will be made between the current hurricane season “enhanced” sounding network in the Caribbean Sea region and what might be possible for the same budget via an adaptive strategy.

Available online at http://ams.confex.com/ams/29Hurricanes/techprogram/MEETING.HTM.

Douglas, M. W., J. F. Mejia, 2010: Testing a low-cost radiosonde system for possible use in adaptive sounding networks. Extended Abstracts, 15th Symposium on Meteorological Observation and Instrumentation, Atlanta, GA, USA, American Meteorological Society, P265.

Recently the National Severe Storms Laboratory obtained a low-cost (~$10K) Intermet 3050 radiosonde system for testing as a possible supplement to existing laboratory systems. The purpose of this testing has been to evaluate the quality of the data from the Intermet radiosondes by compariong these data with data from other radiosondes. Also, we are evaluating the signal strength from the Internet's omni-directional antenna, the system's portability, and different aspects of the software. To date, testing has involved same-balloon ascent comparisons between both NSSL's Vaisala RS-92 radiosondes and National Weather Service Sippican Mark 2 radiosondes. This presentation will describe the procedures used to carry out the comparisons between the different radiosonde sensors and the results. Every one of the nine same-balloon train launches at the Albuquerque NWS radiosonde site in July-August 2009 showed a systematic offset between the humidity values from the Sippican and Intermet sondes, with the Sippican sondes showing lower relative humidities of 5-10% in the lower- through mid- troposphere. However, the differences varied with height. Fewer comparisons have been made between the Vaisala and Intermet sondes to date, but results from this comparison are expected well prior to the AMS Meeting.

Available online at http://ams.confex.com/ams/90annual/techprogram/programexpanded_575.htm.

Douglas, M. W., J. F. Mejia, D. B. Enfield, 2010: Developing an enhanced climate monitoring network for the Inter-American seas region. Extended Abstracts, 14th Symposium on Integrated Observing and Assimilation Systems for the Atmosphere, Oceans, and Land Surface (IOAS-AOLS), Atlanta, GA, USA, American Meteorological Society, 6A.6.

The Intra-Americas Study of Climate Processes (IASCLIP) is a research program that has objectives of improving climate prediction over and bordering the Inter-American Seas region, a region roughly extending from the Gulf of Mexico to northern South America. This region has not been the focus of previous US CLIVAR-supported research activities such as NAME, MESA, and most recently VOCALS.
The IASCLIP domain, although being somewhat well-covered by routine meteorological measurements because of the operational interest in hurricane forecasting, presents complications for developing a climate monitoring network suitable for addressing many research questions. The presence of large islands and complicate land-sea boundaries produces large amplitude and complex local circulations modified by the diurnal cycle of solar heating. Most routine observation sites (either surface or upper-air) are affected by these local influences, leading to uncertainties in the mean over-ocean conditions.
This presentation provides an overview of some measurement needs, logistical complications, and potential observation strategies being considered for both oceanic and atmospheric measurements that will be required for advancing climate research activities in the region.

Available online at http://ams.confex.com/ams/90annual/techprogram/programexpanded_576.htm.

Douglas, M. W., J. F. Mejia, 2010: The recent availability of low-cost radiosonde systems and their implications for adaptive sounding arrays. Extended Abstracts, 15th Symposium on Meteorological Observation and Instrumentation, Atlanta, GA, USA, American Meteorological Society, 9.5.

Available online at http://ams.confex.com/ams/90annual/techprogram/programexpanded_575.htm.

Douglas, M. W., J. F. Mejia, 2010: Evaluating a new low-cost radiosonde system for use in adaptive sounding networks. Extended Abstracts, Lubbock Severe Weather Workshop, Lubbock, TX, USA, National Weather Service, Texas Tech University, ppt file.

Available online at http://lubsvrconf.org/pres_links.php.

Douglas, M. W., J. F. Mejia, 2009: Requirements for developing an adaptive radiosonde network for improved regional weather forecasting over southwestern North America. Extended Abstracts, Fifth Symposium on Southwest Hydrometeorology, Albuquerque, NM, USA, National Weather Service, University of New Mexico, ppt file.

Available online at http://www.srh.noaa.gov/abq/?n=sswhm2009abq.

Engerer, N. A., D. J. Stensrud, M. C. Coniglio, 2008: Surface Characteristics of Observed Cold Pools. Monthly Weather Review, 136, 4839-4849.

Cold pools are a key element in the organization of precipitating convective systems, yet knowledge of their typical surface characteristics is largely anecdotal. To help alleviate this situation, cold pools from 39 mesoscale convective system (MCS) events are sampled using Oklahoma Mesonet surface observations. One thousand three hundred and eighty-nine time series of surface observations are used to determine typical rises in surface pressure and decreases in temperature, potential temperature, and equivalent potential temperature associated with the cold pool, and the maximum wind speeds in the cold pool. The data are separated into one of four convective system lifecycle stages: first storms, MCS initiation, mature MCS, and MCS dissipation. Results indicate that the mean surface pressure rises associated with cold pools increase from 3.2 hPa for the first storms lifecycle stage to 4.5 hPa for the mature MCS stage before dropping to 3.3 hPa for the dissipation stage. In contrast, the mean temperature (potential temperature) deficits associated with cold pools decrease from 9.5 K (9.8 K) to 5.4 K (5.6 K) from the first storms to dissipation stage, with a decrease of approximately 1 K associated with each advance in lifecycle stage. However, the daytime and early evening observations show mean temperature deficits over 11 K. A comparison of these observed cold pool characteristics with results from idealized numerical simulations of MCSs suggests that observed cold pools likely are stronger than those found in model simulations, particularly when ice processes are neglected in the microphysics parameterization. The mean deficits in equivalent potential temperature also decrease with MCS lifecycle stage, starting at 21.6 K for first storms and dropping to 13.9 K for dissipation. Mean wind gusts are above 15 m s-1 for all lifecycle stages. These results should help numerical modelers determine if the cold pools in high-resolution models are in reasonable agreement with the observed characteristics found herein. Thunderstorm simulations and forecasts with thin model layers near the surface also are needed to obtain better representations of cold pool surface characteristics that can be compared with observations.

Feltz, W. F., K. Bah, K. Bedka, J. Gerth, J. S. Kain, S. Lindstrom, J. Otkin, T. Schmidt, J. Sieglaff, C. Siewert, R. Rabin, 2010: UW-CIMSS GOES-R Proving Ground Participation in Storm Prediction Center Hazardous Weather Testbed. Preprints, 17th Conference on Satellite Meteorology and Oceanography, Annapolis, MD, USA, Amer. Meteor. Soc.,, P9.9.

Gilleland, E., M. Pocernich, H. E. Brooks, 2006: Analyzing the Extreme Behavior of Large-Scale Meteorlogical Variables Found To Have Influence on Severe Storms and Tornadic Events Using Global Reanalysis Data. Extended Abstracts, 2006 Joint Statistical Meetings (JSM) of the American Statistical Association (ASA): Statistics for an uncertain world: Meeting global challenges, Seattle, WA, USA, American Statistical Association, 453-453.

Gourley, J. J., Z. L. Flamig, Y. Hong, T. J. Schuur, S. Giangrande, J. A. Vrugt, 2009: Hydrologic Performance of Rainfall Estimates from Polarimetric Radar. Proc. 34th Conference on Radar Meteorology, Williamsburg, VA, USA, American Meteorological Society, P14.18.

Gourley, J. J., D. P. Jorgensen, S. Y. Matrosov, Z. L. Flamig, 2009: Evaluation of incremental improvements to quantitative precipitation estimates in complex terrain. J. Hydrometeor., 10, 1507-1520.

Gourley, J. J., Y. Hong, Z. L. Flamig, L. Li, J. Wang, 2010: Intercomparison of rainfall estimates from radar, satellite, gauge, and combinations for a season of record rainfall. Journal of Applied Meteorology and Climatology, 49, 437-452.

Gourley, J. J., S. E. Giangrande, Y. Hong, Z. L. Flamig, T. J. Schuur, J. A. Vrugt, 2010: Impacts of polarimetric radar observations on hydrologic simulation. J. Hydrometeor., 11, 781-796.

Gourley, J. J., Y. Hong, Z. L. Flamig, J. Wang, H. Vergara, E. N. Anagnostou, 2011: Hydrologic Evaluation of Rainfall Estimates from Radar, Satellite, Gauge, and Combinations on Ft. Cobb Basin, Oklahoma. Journal of Hydrometeorology, 12, 973-988.

This study evaluates rainfall estimates from the Next Generation Weather Radar (NEXRAD), operational rain gauges, Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Cloud Classification System (PERSIANN-CCS) in the context as inputs to a calibrated, distributed hydrologic model. A high-density Micronet of rain gauges on the 342-km2 Ft. Cobb basin in Oklahoma was used as reference rainfall to calibrate the National Weather Service’s (NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM) at 4-km/l-h and 0.25°/3-h resolutions. The unadjusted radar product was the overall worst product, while the stage IV radar product with hourly rain gauge adjustment had the best hydrologic skill with a Micronet relative efficiency score of −0.5, only slightly worse than the reference simulation forced by Micronet rainfall. Simulations from TRMM-3B42RT were better than PERSIANN-CCS-RT (a real-time version of PERSIANN-CSS) and equivalent to those from the operational rain gauge network. The high degree of hydrologic skill with TRMM-3B42RT forcing was only achievable when the model was calibrated at TRMM’s 0.25°/3-h resolution, thus highlighting the importance of considering rainfall product resolution during model calibration.

Grunwald, S., H. E. Brooks, 2011: Relationship between sounding derived parameters and the strength of tornadoes in Europe and the USA from reanalysis data. Atmospheric Research, 100, 479-488.

Proximity soundings from reanalysis data for tornado events in Europe for the years 1958 to 1999 and in the US for the years 1991 to 1999 have been used for generating distributions of parameter combinations important for severe convection. They include parcel updraft velocity (WMAX) and deep-layer shear (DLS), lifting condensation level (LCL) and deep-layer shear (DLS), and LCL and shallow-layer shear (LLS) for weak and significant tornadoes. We investigate how well they discriminate between weak and significant tornadoes. For Europe, these distributions have been generated for unrated, F0 and F1 tornadoes as well to discover if the unrated tornadoes can be associated with the weak tornadoes.
The pattern of parameter combination distributions for unrated tornadoes in Europe strongly resembles the pattern of F0 tornadoes. Thus, the unrated tornadoes are likely to consist of mostly F0 tornadoes. Consequently, the unrated tornadoes have been included into the weak tornadoes and distributions of parameter combinations have been generated for these.
In Europe, none of the three combinations can discriminate well between weak and significant tornadoes, but all can discriminate if the unrated tornadoes are included with the weak tornadoes (unrated/weak). In the US, the combinations of LCL and either of the shear parameters discriminate well between weak and significant tornadoes, with significant tornadoes occurring at lower LCL and higher shear values than the weak ones. In Europe, the shear shows the same behavior, but the LCL behaves differently, with significant tornadoes occurring at higher LCL than the unrated/weak ones. The combination of WMAX and DLS is a good discriminator between unrated/weak and significant tornadoes in Europe, but not in the US, with significant tornadoes occurring at a higher WMAX and DLS than the unrated/weak tornadoes.

Available online at http://www.nssl.noaa.gov/users/brooks/public_html/papers/grunwaldbrooks2011.pdf.

Gutowski, Jr., W. J., G. C. Hegerl, G. J. Holland, T. R. Knutson, L. O. Mearns, R. J. Stouffer, P. J. Webster, M. F. Wehner, F. W. Zwiers, H. E. Brooks, K. A. Emanuel, P. D. Komar, J. P. Kossin, K. E. Kunkel, R. McDonald, G. A. Meehl, R. J. Trapp, 2008: Causes of Observed Changes in Extremes and Projections of Future Changes. Weather and Climate Extremes in a Changing Climate Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands: Synthesis and Assessment Product 3.3 Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change, T. R. Karl, G. A. Meehl, C. D. Miller, S. J. Hassol, A. M. Waple, W. L. Murray, Ed(s)., U.S. Climate Change Science Program and the Subcommittee on Glob, 81-116.

Heinselman, P., S. Weiss, M. Coniglio, D. Andra, G. Stumpf, B. Phillips, J. Brotzge, cited 2008: 2008 Spring HWT Experiments at the NWC. [Available online at ://http://www.nwas.org/newsletters/pdf/news_october2008.pdf.]

Higgins, W., D. Ahijevych, J. Amador, A. Barros, E. Berbery, E. Caetano, R. Carbone, P. Ciesielski, R. Cifelli, M. Cortez-Vazquez, A. Douglas, M. Douglas, G. Emmanuel, C. Fairall, D. Gochis, D. Gutzler, T. Jackson, R. Johnson, C. King, T. Lang, M. Lee, D. Lettenmaier, R. Lobato, V. Magaña, J. Meitin, K. Mo, S. Nesbitt, F. Ocampo-Torres, E. Pytlak, P. Rodgers, S. Rutledge, J. Schemm, S. Schubert, A. White, C. Williams, A. Wood, R. Zamora, C. Zhang, 2006: The NAME 2004 Field Campaign and Modeling Strategy. Bulletin of the American Meteorological Society, 87, 79-94.

Hoekstra, S., K. Klockow, R. Riley, J. Brotzge, H. Brooks, 2011: A Preliminary Look at the Social Perspective of Warn-on-Forecast: Preferred Tornado Warning Lead Time and the General Public's Perceptions of Weather Risks. Weather, Climate, and Society, 3, 128-140.

Tornado warnings are currently issued an average of 13 minutes in advance of a tornado (Golden and Adams 2000) and are based on a warn-on-detection paradigm (Erickson and Brooks 2006). However, computer model improvements may allow for a new warning paradigm, warn-on- forecast, to be established in the future (Stensrud et al. 2009). This would mean that tornado warnings could be issued one to two hours in advance, prior to storm initiation. In anticipation of the technological innovation, this study inquires whether the “warn-on-forecast” paradigm for tornado warnings may be preferred by the public (i.e., individuals and single families). Our sample is drawn from visitors to the National Weather Center in Norman, Oklahoma. During the summer and fall of 2009, surveys were distributed to 320 participants to assess their understanding and perception of weather risks and preferred tornado warning lead-time.

Responses were analyzed according to several different parameters including age, region of residency, educational level, number of children, and prior tornado experience. A majority of the respondents answered many of the weather risk questions correctly. They seemed to be familiar with tornado seasons; however, they were unaware of the relative number of fatalities caused by tornadoes and several additional weather phenomena each year in the United States. The preferred lead-time was 34.3 minutes according to average survey responses. This suggests that while the general public may currently prefer a longer average lead-time than the present system offers, the preference does not extend to the one to two hour time-frame theoretically offered by the warn-on-forecast system. When asked what they would do if given a one-hour lead-time, respondents reported that taking shelter was a lesser priority than when given a 15-minute leadtime, and fleeing the area became a slightly more popular alternative. A majority of respondents also reported the situation would feel less life threatening if given a one-hour lead-time. These results suggest that how the public responds to longer lead times may be complex and situationally-dependent, and further study must be conducted to ascertain the users for whom the longer lead-times would carry the most value. These results form the basis of an informative stated-preference approach to predicting public response to long (> 1 hour) warning lead times, using public understanding of the risks posed by severe weather events to contextualize leadtime demand.

Jensen, T., B. Brown, M. C. Coniglio, J. S. Kain, S. J. Weiss, L. Nance, 2010: Evaluation of experimental forecasts from the 2009 NOAA Hazardous Weather Testbed Spring Experiment using both traditional and spatial methods. Preprints, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., 527.

Kain, J. S., S. J. Weiss, J. J. Levit, M. E. Baldwin, D. R. Bright, 2006: Examination of convection-allowing configurations of the WRF model for the prediction of severe convective weather: The SPC/NSSL Spring Program 2004. Weather and Forecasting, 21, 167-181.

Convection-allowing configurations of the Weather Research and Forecast (WRF) model were evaluated during the 2004 Storm Prediction Center–National Severe Storms Laboratory Spring Program in a simulated severe weather forecasting environment. The utility of the WRF forecasts was assessed in two different ways. First, WRF output was used in the preparation of daily experimental human forecasts for severe weather. These forecasts were compared with corresponding predictions made without access to WRF data to provide a measure of the impact of the experimental data on the human decision-making process. Second, WRF output was compared directly with output from current operational forecast models. Results indicate that human forecasts showed a small, but measurable, improvement when forecasters had access to the high-resolution WRF output and, in the mean, the WRF output received higher ratings than the operational Eta Model on subjective performance measures related to convective initiation, evolution, and mode. The results suggest that convection-allowing models have the potential to provide a value-added benefit to the traditional guidance package used by severe weather forecasters.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, D. B. Weber, K. W. Thomas, 2007: Some practical considerations for the first generation of operational convection-allowing NWP: How much resolution is enough?. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.5.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, D. B. Weber, K. W. Thomas, 2008: Some practical considerations regarding horizontal resolution in the first generation of operational convection-allowing NWP. Weather and Forecasting, 23, 931-952.

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment two different highresolution
configurations of the WRF-ARW model were used to produce 30 h forecasts five days
a week for a total of 7 weeks. These configurations used the same physical parameterizations and
the same input dataset for initial and boundary conditions, differing primarily in their spatial resolution.
The first set of runs used 4 km horizontal grid spacing with 35 vertical levels while the
second used 2 km grid spacing and 51 vertical levels.
Output from these daily forecasts is analyzed to assess the numerical forecast sensitivity to
spatial resolution in the upper end of the convection-allowing range of grid-spacing. The analysis
is based on a combination of visual comparison, systematic subjective verification conducted during
the Spring Experiment, and objective metrics based largely on the mean diurnal cycle of simulated
reflectivity and precipitation fields. Additional insight is gained by examining the size
distributions of individual reflectivity and precipitation entities and by comparing forecasts of
mesoscyclone characteristics in the two sets of forecasts.
In general, the 2 km forecasts provide more detailed presentations of convective activity, but
there appears to be little, if any, forecast skill on the scales where the added details emerge. On
the scales where both model configurations show higher levels of skill - the scale of mesoscale
convective features - the forecasts appear to provide comparable utility for severe weather forecasters.
These results suggest that 4 km grid spacing is a good place to start for the first generation
of 1-2 day convection-permitting operational NWP.

Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, J. J. Levit, G. W. Carbin, C. S. Schwartz, M. L. Weisman, K. K. Droegemeier, 2007: Some practical considerations for the first generation of operational convection-allowing NWP: How much resolution is enough?. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.5. [Available from John S. Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment (formerly known as the SPC/NSSL Spring Program) two different high-resolution configurations of the WRF-ARW model were used to produce 30 h forecasts five days a week for a total of 7 weeks. These configurations used the same physical parameterizations and the same input dataset for initial and boundary conditions, differing primarily in their spatial resolution. The first set of runs used 4 km horizontal grid spacing with 35 vertical levels while the second used 2 km grid spacing and 51 vertical levels.

This setup provided an unprecedented opportunity to assess the sensitivity to spatial resolution in the upper end of the convection-allowing range of grid-spacing, during many different severe-weather events. Of particular interest was whether the ~ ten fold increase in computing expense required by the 2 km runs could be justified by added value in the higher resolution forecasts. In this study, we examine and compare these forecasts from several different perspectives. First, we provide a visual examination of simulated reflectivity fields from selected convective events, highlighting the differences that might be detected by an operational forecaster – differences between the two model runs and the ways that both differ from observed reflectivity fields. Next, we present the results of subjective assessments of forecast skill, based on daily ratings assigned by panels of experts during the Spring Experiment. Then, we move on to objective measures of skill. These measures are based on time-averaged behavior characteristics of the models rather than selected points in time and space. For example, we examine the mean diurnal trends of simulated reflectivity and accumulated precipitation fields, as compared with observations. We compare the size distributions of individual reflectivity and precipitation entities, or “storms”, and we look at measures of storm rotation. Further, we look at traditional verification statistics such as equitable-threat and bias scores.

In general, we find that meteorological fields from the two model configurations behave much more like each other than like observations. The 2 km forecasts provide more detailed structures and appear to provide more realistic depictions of supercell-like storm configurations, both of which are intriguing to severe weather forecasters, but neither configuration shows much skill in predicting these small-scale features. On the scales where they show higher levels of skill – the scale of mesoscale convective features – the forecasts are often quite similar. The implications of these results, i.e., the value added by doubling resolution in this context, will be discussed at the conference.

Available online at http://ams.confex.com/ams/pdfpapers/124513.pdf.

Kain, J. S., S. J. Weiss, S. R. Dembek, J. J. Levit, D. R. Bright, J. L. Case, M. C. Coniglio, A. R. Dean, R. Sobash, 2008: Severe-weather forecast guidance from the first generation of large domain convection-allowing models: Challenges and opportunities. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor Soc., CD-ROM, 12.1. [Available from John Kain, NSSL, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

Kain, J. S., S. J. Weiss, M. E. Baldwin, 2006: The value of collaboration between researchers and forecasters in the development of NWP models. Preprints, The 4th Joint Korea-U. S. Workshop on Mesoscale Observation, Data Assimilation, and Modeling for Severe Weather, Seoul, Republic of Korea, Korea Science and Engineering Foundation/U.S. National Science F, 6.5. [Available from John Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Kain, J. S., S. J. Weiss, M. E. Baldwin, 2006: The value of collaboration between researchers and forecasters in the development of NWP models. Preprints, The 4th Joint Korea-U. S. Workshop on Mesoscale Observation, Data Assimilation, and Modeling for Severe Weather, Seoul, Republic of Korea, Korea Science and Engineering Foundation/U.S. National Science F, 6.5. [Available from John Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Kain, J. S., M. Xue, M. C. Coniglio, S. J. Weiss, F. Kong, T. L. Jensen, B. G. Brown, J. Gao, K. Brewster, K. W. Thomas, Y. Wang, C. S. Schwartz, J. J. Levit, 2010: Assessing advances in the assimilation of radar data within a collaborative forecasting-research environment. Weather and Forecasting, 25, 1510-1521.

The impacts of assimilating radar data and other mesoscale observations in real-time, convection-allowing model forecasts were evaluated during the spring seasons of 2008 and 2009 as part of the Hazardous Weather Test Bed Spring Experiment activities. In tests of a prototype continental U.S.-scale forecast system, focusing primarily on regions with active deep convection at the initial time, assimilation of these observations had a positive impact. Daily interrogation of output by teams of modelers, forecasters, and verification experts provided additional insights into the value-added characteristics of the unique assimilation forecasts. This evaluation revealed that the positive effects of the assimilation were greatest during the first 3–6 h of each forecast, appeared to be most pronounced with larger convective systems, and may have been related to a phase lag that sometimes developed when the convective-scale information was not assimilated. These preliminary results are currently being evaluated further using advanced objective verification techniques.

Kain, J. S., S. R. Dembek, S. J. Weiss, J. L. Case, J. J. Levit, R. A. Sobash, 2010: Extracting unique information from high resolution forecast models: Monitoring selected fields and phenomena every time step. Weather and Forecasting, 25, 1536-1542.

A new strategy for generating and presenting model diagnostic fields from convection-allowing forecast models is introduced. The fields are produced by computing temporal-maximum values for selected diagnostics at each horizontal grid point between scheduled output times. The two-dimensional arrays containing these maximum values are saved at the scheduled output times. The additional fields have minimal impacts on the size of the output files and the computation of most diagnostic quantities can be done very efficiently during integration of the Weather Research and Forecasting Model. Results show that these unique output fields facilitate the examination of features associated with convective storms, which can change dramatically within typical output intervals of 1–3 h.

Killeen, T. J., M. W. Douglas, T. Consiglio, P. M. Jorgensen, J. F. Mejia, 2007: Dry Spots and Wet Spots in the Andean hotspot. Journal of Biogeography, 34, 1357-1373.

Aim To explain the relationship between topography, prevailing winds and precipitation in order to identify regions with contrasting precipitation regimes and then compare floristic similarity among regions in the context of climate change.

Location Eastern slope of the tropical Andes, South America.

Methods We used information sources in the public domain to identify the relationship between geology, topography, prevailing wind patterns and precipitation. Areas with contrasting precipitation regimes were identified and compared for their floristic similarity.

Results We identify spatially separate super-humid, humid and relatively dry regions on the eastern slope of the Andes and show how they are formed by the interaction of prevailing winds, diurnally varying atmospheric circulations and the local topography of the Andes. One key aspect related to the formation of these climatically distinct regions is the South American low-level jet (SALLJ), a relatively steady wind gyre that flows pole-ward along the eastern slopes of the Andes and is part of the gyre associated with the Atlantic trade winds that cross the Amazon Basin. The strongest winds of the SALLJ occur near the 'elbow of the Andes' at 18° S. Super-humid regions with mean annual precipitation greater than 3500 mm, are associated with a 'favourable' combination of topography, wind-flow orientation and local air circulation that favours ascent at certain hours of the day. Much drier regions, with mean annual precipitation less than 1500 mm, are associated with 'unfavourable' topographic orientation with respect to the mean winds and areas of reduced cloudiness produced by local breezes that moderate the cloudiness. We show the distribution of satellite-estimated frequency of cloudiness and offer hypotheses to explain the occurrence of these patterns and to explain regions of anomalously low precipitation in Bolivia and northern Peru. Floristic analysis shows that overall similarity among all circumscribed regions of this study is low; however, similarity among super-humid and humid regions is greater when compared with similarity among dry regions. Spatially separate areas with humid and super-humid precipitation regimes show similarity gradients that are correlated with latitude (proximity) and precipitation.

Main conclusions The distribution of precipitation on the eastern slope of the Andes is not simply correlated with latitude, as is often assumed, but is the result of the interplay between wind and topography. Understanding the phenomena responsible for producing the observed precipitation patterns is important for mapping and modelling biodiversity, as well as for interpreting both past and future climate scenarios and the impact of climate change on biodiversity. Super-humid and dry regions have topographic characteristics that contribute to local climatic stability and may represent ancestral refugia for biodiversity; these regions are a conservation priority due to their unique climatic characteristics and the biodiversity associated with those characteristics.

Kong, F., M. XUE, D. R. Bright, M. C. Coniglio, K. W. Thomas, Y. Wang, D. Weber, J. S. Kain, S. J. Weiss, J. Du, 2007: Preliminary analysis on the real-time storm-scale ensemble forecasts produced as a part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment.. Preprints, Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc, CD-ROM, 3B.2.

Kong, F., M. Xue, D. R. Bright, M. C. Coniglio, K. W. Thomas, Y. Wang, D. B. Weber, J. S. Kain, S. J. Weiss, J. Du, 2007: Preliminary analysis on the real-time storm-scale ensemble forecasts produced as a part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.2. [Available from Fanyou Kong, CAPS, 120 David L. Boren Blvd., Norman, OK, USA, 73072.]

A real-time storm-scale WRF-ARW-based ensemble forecast system at 4-km resolution is being developed at CAPS and will be run daily for 33 hours as part of the NOAA Hazardous Weather Testbed (HWT) 2007 Spring Experiment, for a domain covering the eastern 2/3 of the continental U.S. This pilot system consists of ten hybrid perturbation members that consist of a combination of perturbed initial conditions and various microphysics and PBL physics parameterization schemes. The design considerations and the scientific questions that the system intends to address will be presented and discussed.

In addition to traditional ensemble products widely used in large-scale and mesoscale ensemble forecasting systems, such as the mean, spread, and probability of selected forecast fields, emphases are given to the generation and assessment of products specific to storm-scale, cloud-resolving ensemble forecasts. Such products include but are not limited to: probability of storm type (e.g., linear vs. cellular), large hail probability, icing potential (high super-cooled water content probability), damaging wind gusts at surface, reflectivity exceedance, updraft rotation, and supercell thunderstorm detection in the form of probability or joint probability for Supercell Composite Parameter, Significant Tornado Parameter, Supercell Detection Index, and Updraft Helicity. Many of these products are created in real time through existing capabilities in the SPC version of the N-AWIPS system for the use and evaluation by researchers and operational forecasters during the experiment. The statistical consistency of the ensemble system, in terms of spread-error relation, is assessed using the two-months of data after the experiment. The performance of the ensemble forecasts, in terms of quantitative skill scores, is compared with the NCEP operational SREF and 12 km NAM forecasts, and a CAPS 2-km WRF forecast over the same domain and period. Skill scores for sub-groups of the ensemble will be examined to assess the effectiveness of initial condition and physics perturbations.

Available online at http://ams.confex.com/ams/pdfpapers/124667.pdf.

Kong, F., M. Xue, K. W. Thomas, Y. Wang, J. S. Kain, S. J. Weiss, D. R. Bright, J. Du, K. K. Droegemeier, 2008: Real-Time Storm-Scale Ensemble Forecast 2008 Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.3. [Available from Fanyou Kong, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_141827.htm.

Kong, F., M. Xue, K. W. Thomas, Y. Wang, K. A. Brewster, J. Gao, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2009: A real-time storm-scale ensemble forecast system: 2009 Spring Experiment. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 16A.3. [Available from Fanyou Kong, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154118.htm.

Krehbiel, P., W. Rison, R. Thomas, D. MacGorman, W. D. Rust, T. Marshall, M. Stolzenburg, 2006: A review of lightning phenomenology in thunderstorms. Preprints, 2nd Conference on Meteorological Applications of Lightning Data, Atlanta, GA, USA, American Meteorological Society, 6.2.

Kunkel, K. E., P. Bromirski, H. E. Brooks, T. Cavazos, A. V. Douglas, D. R. Easterling, K. A. Emanuel, P. Y. Groisman, G. J. Holland, T. R. Knutson, J. P. Kossin, P. D. Komar, D. H. Levinson, R. L. Smith, J. Allan, R. Assel, S. Changnon, J. Lawrimore, K. B. Liu, T. Peterson, 2008: Observed Changes in Weather and Climate Extremes. Weather and Climate Extremes in a Changing Climate. Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands. Synthesis and Assessment Product 3.3 Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change, T. M. Karl, G. A. Meehl, C. D. Miller, S. J. Hassol, A. M. Waple, W. L. Murray, Ed(s)., U.S. Climate Change Science Program and the Subcommittee on Glob, 35-80.

Lakshmanan, V., J. J. Gourley, Z. Flamig, S. Giagrande, 2009: A simple data-driven model for streamflow prediction. Preprints, 6th Conference on Artificial Applications to the Environmental Sciences, Phoenix, AZ, USA, Amer. Meteor. So, CD-ROM, J6.2.

Lakshmanan, V., J. Kain, 2010: A Gaussian Mixture Model Approach to Forecast Verification. Weather and Forecasting, 25, 908-920.

Verification methods for high-resolution forecasts have been based either
on filtering or on objects created by thresholding the images.
The filtering methods do not easily permit the use of
deformation while identifying objects based on thresholds can be problematic.
In this paper, we introduce a new approach in which the
observed and forecast fields are broken down into a mixture of Gaussians, and
the parameters of the Gaussian Mixture Model fit are examined
to identify translation, rotation and scaling errors.
We discuss the advantages of this method in
terms of the traditional filtering or object-based methods and
interpret resulting scores on a standard verification dataset.

Available online at http://cimms.ou.edu/~lakshman/Papers/gmmverif.pdf.

Lakshmanan, V., J. S. Kain, 2010: Model Verification Using Gaussian Mixture Models. Preprints, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., 6.4.

Lakshmanan, V., J. Kain, 2010: A Gaussian mixture model approach to forecast verification. Weather and Forecasting, 25, 908-920.

We introduce a new approach in which the observed and forecast fields are broken down into a mixture of Gaussians and the parameters of the Gaussian Mixture Model fit are examined to identify translation, rotation and scaling errors. We discuss the advantages of this method in terms of the traditional filtering or object-based methods and interpret resulting scores on a standard verification dataset.

Available online at http://cimms.ou.edu/%7Elakshman/Papers/gmmverif.pdf.

Lakshmanan, V., j. Kain, 2010: Model verification using gaussian mixture models. Extended Abstracts, 20th Conference on Probability and Statistics in the Atmospheric Sciences, Atlanta, GA, USA, Amer. Meteor. Soc., CD-ROM, 6.4.

Lakshmanan, V., R. Rabin, J. Otkin, J. Kain, 2012: Approximating radiative transfer with a neural network. Preprints, 10th Conf. on Artificial Intelligence App. to Env. Sci., Norman, OK, USA, AMS, CD-ROM, TJ14.3.

We demonstrate that it is possible to approximate the radiative transfer model using an universal approximator whose parameters can be determined by fitting the output of the forward model to inputs derived from the model forecasts from which it was computed. The resulting approximation is very close to the complex radiative transfer model and has the advantage that it can be computed in a matter of minutes. This approximation is carried out on model forecasts to demonstrate its utility as a visualization and forecasting tool.

Lakshmanan, V., R. Rabin, J. Kain, J. Otkin, S. Dembek, 2012: Visualizing Model Data Using A Fast Approximation of a Radiative Transfer Model. Journal of Atmospheric and Oceanic Technology, 29, 745-754.

Visualizing model forecasts using simulated satellite imagery has proven very useful because the depiction of forecasts using cloud imagery can provide inferences about meteorological scenarios and
physical processes that are not characterized well by depictions of those forecasts using radar reflectivity. A forward radiative transfer model is capable of providing such a visible-channel depiction of numerical weather prediction model output, but present-day forward models are too slow to run routinely on operational model forecasts.

It is demonstrated that it is possible to approximate the radiative transfer model using an universal approximator whose parameters can be determined by fitting the output of the forward model to inputs derived from the raw output from the prediction model. The resulting approximation is very close to the result derived from the complex radiative transfer model and has the advantage that it can be computed in a
small fraction of the time required by the forward model. This approximation is carried out on model forecasts to demonstrate its utility as a visualization and forecasting tool.

Available online at http://cimms.ou.edu/~lakshman/Papers/visnn.pdf.

Lengyel, M., M. A. Cooper, R. Holle, H. E. Brooks, 2010: The role of multidisciplinary teams and public education in reducing lightning casualties worldwide. Proc. 30th International Conference on Lightning Protection, Cagliari, Italy, IEEE, SSB-1329. [Available from macooper@uic.edu,

In the past century, lightning killed more people in the United States on average annually than any other storm situation except floods. However, due to persistent lightning safety efforts by a multidisciplinary team, the annual National Lightning Safety Awareness Week campaign, shifts in population from rural to urban areas, and improved grounding of buildings, US lightning deaths have decreased to an average of less than 50 per year over the past decade. This demonstrates that aggressive public education can have a significant role in reducing lightning deaths and injuries.

Liang, X. Z., M. Xu, K. E. Kunkel, G. A. Grell, J. S. Kain, 2007: Regional Climate Model Simulation of U.S.–Mexico Summer Precipitation Using the Optimal Ensemble of Two Cumulus Parameterizations. Journal of Climate, 20, 5201-5207.

Marsh, P. T., H. E. Brooks, D. J. Karoly, 2007: Assessment of the severe weather environment in North America simulated by a global climate model. Atmospheric Science Letters, 8, 106.

Annual and seasonal cycles of convectively important atmospheric parameters for North America have been computed using the Community Climate System Model version 3 (CCSM3) Global Climate Model using a decade of CCSM3 data. Results for the spatial and temporal distributions of environments conducive to severe convective weather qualitatively agree with observational estimates from NCAR/NCEP global reanalyses, although the model underestimates the frequency of occurrence of severe weather environments. This result demonstrates the possibility for future studies aimed at determining possible changes in the distribution of severe weather environments associated with global climate change.

Marsh, P. T., H. E. Brooks, D. J. Karoly, 2009: Preliminary investigation into the severe thunderstorm environment of Europe simulated by the Community Climate System Model 3. Atmospheric Research, 93, 607-618.

Seasonal cycles of parameters conducive for the development of severe thunderstorms were computed using 20 years of output from the Community Climate System Model v3 (CCSM3) for both a 20th century simulation and a 21st century simulation. These parameters were compared against parameters calculated from the NCEP/NCAR Global Reanalysis data, which are of similar resolution. The CCSM3's current simulation produced seasonal and spatial distributions of both mean CAPE and favorable severe environments that were qualitatively similar to the NCEP/NCAR Global Reanalysis, although the CCSM3 underestimates the frequency of severe thunderstorm environments. Preliminary comparisons of the CCSM3's 21st century simulation under the IPCC's A2 emissions scenario to the 20th century simulation indicated a slight increase in mean CAPE in the cool season and a slight decrease in the warm season and little change in mean wind shear. However, there was a small increase in favorable severe environments for most locations resulting from an increase in the joint occurrence of high CAPE and high deep layer shear. Regions near the Mediterranean Sea experienced the biggest increase in both mean CAPE and favorable severe environments, regions near the Faeroe Islands experienced an increase in only seasonal mean CAPE, and regions across northern Europe experienced little change.

Marsh, P. T., J. S. Kain, S. J. Weiss, I. L. Jirak, R. A. Sobash, F. Kong, K. W. Thomas, M. Xue, 2010: INVESTIGATING A FUNDAMENTAL COMPONENT OF A WARN-ON FORECAST SYSTEM IN A COLLABORATIVE REAL-TIME EXPERIMENT. Extended Abstracts, 11th Severe Local Storms Conference, Denver, CO, USA, American Meteorological Society, 14.4.

The Warn-on-Forecast paradigm (WoF) envisions probabilistic prediction of severe convective phenomena based on ensemble forecasts using high-resolution models. One of many scientific challenges facing Warn-on-Forecast is how to construct reliable probabilistic information regarding severe convective phenomena when these phenomena will not be explicitly resolvable for many years to come. One approach to address this issue is to identify “extreme” model-generated features that have strong correlations with observed extreme convective phenomena, and then use the former as surrogates for the extreme phenomena in question. This “surrogate-severe” (SS) approach is fundamentally different from traditional applications of NWP for severe weather because it is phenomenon based. In particular, it relies on identification of explicit convective phenomena rather than environmental conditions to predict the likelihood of severe thunderstorms.

Sobash et al. (2009) established the viability of this approach using several different SS diagnostic quantities. Their work used a “neighborhood” approach based on the concepts in Theis et al. (2005) and Brooks et al. (1998) to produce severe-weather probability forecasts based on the locations of SS features in a deterministic model. In the current study, we extend the concepts developed by Sobash et al. (2009) to a 26-member storm-scale ensemble. This ensemble was produced by the Center for Analysis and Prediction of Storms (CAPS) during the 2010 NOAA HWT Spring Experiment. In the ensemble-based application it was found that interpretation of derived probabilistic forecasts depends strongly on the parameters used for post-processing. This presentation examines examples of various derived products, their potential utility for current Outlook-scale severe weather forecasts, and their possible application within the focused scales of WoF for severe weather.

References:
Brooks, H. E., M. Kay, and J. A. Hart, 1998: Objective limits on forecasting skill of rare events. Preprints, 19th Conference on Severe Local Storms, Minneapolis, Minnesota, Amer. Meteor. Soc., 552-555.

Sobash, R. A., J. S. Kain, D. R. Bright, A. R. Dean, M. C. Coniglio, S. J. Weiss, and J. J. Levit, 2009: Forecast guidance for severe thunderstorms based on identification of extreme phenomena in convection-allowing model forecasts. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Amer. Meteor. Soc., Omaha, NE. CD-ROM 4B.6

Theis, S. E., A. Hense, and U. Damrath, 2005: Probabilistic precipitation forecasts from a deterministic model: A pragmatic approach. Meteor. Appl., 12, 257–268.

Available online at http://ams.confex.com/ams/25SLS/techprogram/paper_176218.htm.

Marsh, P. T., J. S. Kain, V. Lakshmanan, A. J. Clark, N. M. Hitchens, J. Hardy, 2012: A Method for Calibrating Deterministic Forecasts of Rare Events. Weather and Forecasting, 27, 531-538.

Convection-allowing models offer forecasters unique insight into convective hazards relative to numerical models using parameterized convection. However, methods to best characterize the uncertainty of guidance derived from convection-allowing models are still unrefined. This paper proposes a method of deriving calibrated probabilistic forecasts of rare events from deterministic forecasts by fitting a parametric kernel density function to the model’s historical spatial error characteristics. This kernel density function is then applied to individual forecast fields to produce probabilistic forecasts.

Marsh, P. T., H. E. Brooks, 2012: Comments on “Tornado Risk Analysis: Is Dixie Alley an Extension of Tornado Alley?”. Bulletin of the American Meteorological Society, 93, 405-407.

McFarquhar, G. M., S. Ghan, J. Verlinde, A. Korolev, J. W. Strapp, B. Schmid, J. Tomlinson, M. Wolde, S. Brooks, D. Cziczo, M. Dubey, J. Fan, C. Flynn, I. Gultepe, J. Hubbe, M. Gilles, A. Laskin, P. Lawson, W. R. Leaitch, P. Liu, X. Liu, D. Lubin, C. Mazzoleni, A. M. Macdonald, R. Moffet, H. Morrison, M. Ovtchinnikov, M. D. Shupe, D. D. Turner, S. Xie, A. Zelenyuk, K. Bae, M. Freer, A. Glen, 2011: Indirect and semi-direct aerosol campaign (ISDAC): The impact of Arctic aerosols on clouds. Bulletin of the American Meteorological Society, 92, 183-201.

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the arctic boundary layer in the vicinity of Barrow, Alaska was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) sponsored by the Department of Energy Atmospheric Radiation Measurement (ARM) and Atmospheric Science Programs. The primary aim of ISDAC was to examine effects of aerosols on clouds that contain both liquid and ice water for clean and polluted environments. ISDAC utilized the ARM permanent observational facilities at Barrow. These include a cloud radar, a polarized micropulse lidar, and an atmospheric emitted radiance interferometer as well as instruments specially deployed for ISDAC measuring aerosol, ice fog, precipitation and spectral shortwave radiation. The National Research Council of Canada Convair-580 flew 27 sorties during ISDAC, collecting data using an unprecedented 42 state-of-the-art cloud and aerosol instruments for more than 100 hours on 12 different days. Data were obtained on a number of days, including above, below and within single- layer stratus on 8 April and 26 April 2008. These data enable a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds influenced by different surface conditions and aerosol loads. Observations acquired on a heavily polluted day, 19 April 2008, are enhancing this understanding. Data acquired in cirrus on transit flights between Fairbanks and Barrow are improving our understanding of the performance of cloud probes in ice. Ultimately the ISDAC data will be used to improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales and pollution regimes, and to determine the extent to which long-term surface-based measurements can provide retrievals of aerosols, clouds, precipitation and radiative heating in the Arctic.

Morss, R. E., J. K. Lazo, B. G. Brown, H. E. Brooks, P. T. Ganderton, B. N. Mills, 2008: Societal and Economic Research and Applications For Weather Forecasts: Priorities for the North American THORPEX Program. Bulletin of the American Meteorological Society, 89, 335-346.

Despite the meteorological community's long-term interest in weather–society interactions, efforts to understand socioeconomic aspects of weather prediction and to incorporate this knowledge into the weather prediction system have yet to reach critical mass. This article aims to reinvigorate interest in societal and economic research and applications (SERA) activities within the meteorological and social science communities by exploring key SERA issues and proposing SERA priorities for the next decade.

The priorities were developed by the authors, building on previous work, with input from a diverse group of social scientists and meteorologists who participated in a SERA workshop in August 2006. The workshop was organized to provide input to the North American regional component of THORPEX: A Global Atmospheric Research Programme, but the priorities identified are broadly applicable to all weather forecast research and applications.

To motivate and frame SERA activities, we first discuss the concept of high-impact weather forecasts and the chain from forecast creation to value realization. Next, we present five interconnected SERA priority themes—use of forecast information in decision making, communication of forecast uncertainty, user-relevant verification, economic value of forecasts, and decision support—and propose research integrated across the themes.

SERA activities can significantly improve understanding of weather–society interactions to the benefit of the meteorological community and society. However, reaching this potential will require dedicated effort to bring together and maintain a sustainable interdisciplinary community.

Ortega, K. L., P. T. Marsh, K. A. Scharfenberg, K. L. Manross, 2011: Populations at risk: Estimating the number of people in the path of 27 April 2011. Preprints, 36th Annual Meeting of the National Weather Association, Birmingham, AL, USA, National Weather Association, P1.27.

Tornado outbreaks can be evaluated in numerous ways. Typically, an outbreak is ranked by number of tornadoes, strength of the tornadoes, the number of fatalities or some combination. Warning effectiveness is usually implied through traditional POD/FAR measures and by the number of injuries or fatalities.

We will investigate using gridded population data to estimate the populations affected by tornadoes and warnings. Population estimates could help in ranking and evaluating not only the outbreak itself, but also warning effectiveness.

Parker, D. J., M. W. Douglas, M. Christoph, A. H. Fink, S. Janicot, J. B. Ngamini, E. Afiesimama, A. Agusti-Panareda, A. Beljaars, F. Dide, A. Ddiedhiou, T. Lebel, J. Polcher, J. L. Redelsperger, C. Thorncroft, G. Wilson, 2008: The Amma radiosonde programme and its implications for the future of atmospheric monitoring over Africa.. Preprints, 28th Conference on Hurricanes and Tropical Meteorology, Orlando, FL, USA, American Meteorological Society, 3C.1.

This presentation describes the upper air observational programme which is being carried out as part of the African Monsoon Multidisciplinary Analysis (AMMA). An important goal of AMMA is to evaluate the impact of the upper-air data on weather and climate prediction for West Africa, and for the hurricane genesis regions of the tropical Atlantic. Since 2004, AMMA scientists have been working with operational agencies in Africa to reactivate silent radiosonde stations, to renovate unreliable stations, and to install new stations in regions of particular climatic importance. A comprehensive upper air network of 21 stations, including four GCOS Upper Air Network (GUAN) stations, is now active over West Africa, and during the AMMA Special Observing Period (SOP) June to September 2006 some 7000 soundings were made in the region, representing the greatest density of upper air observations ever since in the region, exceeding even the number of soundings made during the GATE programme of 1974. AMMA also encompassed a short, intensive campaign on a network of PILOT stations in the western part of the region, centered on Senegal. This activity both exposed the dilapidated state of the operational PILOT network in the region, and demonstrated that important upper air data can be collected at relatively low cost through PILOT soundings. Many operational lessons were learned in AMMA, involving technical problems in the harsh environment of sub-Saharan Africa and issues of funding, coordination and communication among the many nations and agencies involved. From these lessons we are able to make firm recommendations for the maintenance and operation of a useful upper air network in WMO Region I in the future.

Parker, D. J., A. Fink, S. Janicot, J. Ngamini, M. W. Douglas, E. Afiesimama, A. Agusti-Panareda, A. Beljaars, F. Dide, A. Diedhiou, T. Lebel, J. Polcher, J. L. Redelsperger, C. Thorncroft, G. A. Wilson, 2008: The Amma Radiosonde Program and its Implications for the Future of Atmospheric Monitoring Over Africa. Bulletin of the American Meteorological Society, 89, 1015-1027.

This article describes the upper-air program, which has been conducted as part of the African Monsoon Multidisciplinary Analysis (AMMA). Since 2004, AMMA scientists have been working in partnership with operational agencies in Africa to reactivate silent radiosonde stations, to renovate unreliable stations, and to install new stations in regions of particular climatic importance. A comprehensive upper-air network is now active over West Africa and has contributed to high-quality atmospheric monitoring over three monsoon seasons. During the period June to September 2006 high-frequency soundings were performed, in conjunction with intensive aircraft and ground-based activities: some 7,000 soundings were made, representing the greatest density of upper air measurements ever collected over the region. An important goal of AMMA is to evaluate the impact of these data on weather and climate prediction for West Africa, and for the hurricane genesis regions of the tropical Atlantic. Many operational difficulties were encountered in the program, involving technical problems in the harsh environment of sub-Saharan Africa and issues of funding, coordination, and communication among the many nations and agencies involved. In facing up to these difficulties, AMMA achieved a steady improvement in the number of soundings received by numerical weather prediction centers, with a success rate of over 88% by August 2007. From the experience of AMMA, we are therefore able to make firm recommendations for the maintenance and operation of a useful upper-air network in WMO Region I in the future.

Rauhala, J., H. E. Brooks, D. M. Schultz, 2012: Tornado Climatology of Finland. Monthly Weather Review, 140, 1446-1456.

A tornado climatology for Finland is constructed from 1796 to 2007. The climatology consists of two datasets. A historical dataset (1796-1996) is largely constructed from newspaper archives and other historical archives and datasets, and a recent dataset (1997-2007) is largely constructed from eyewitness accounts sent to the Finnish Meteorological Institute and news reports. This article describes the process of collecting and evaluating possible tornado reports. Altogether, 298 Finnish tornado cases comprise the climatology: 129 from the historical dataset and 169 from the recent dataset. An annual average of 14 tornado cases occur in Finland (1997-2007).
A case with a significant tornado (F2 or stronger) occurs in our database on average every other year, comprising 14% of all tornado cases. All documented tornadoes in Finland have occurred between April and November. As in the neighbouring countries in northern Europe, July and August are the months with the maximum frequency of tornado cases, coincident with the highest lightning occurrence both over land and sea. Waterspouts tend to be favored later in the summer, peaking in August. The peak month for significant tornadoes is August. The diurnal peak for tornado cases is 1700-1859 local time.

Scharfenberg, K. A., D. L. Andra, P. T. Marsh, K. L. Ortega, J. Brotzge, 2010: Tornado warning services for misoscale circulations in quasilinear convective systems. Extended Abstracts, 11th Severe Local Storms Conference, Denver, CO, USA, American Meteorological Society, P4.5.

Although long known to exist, misoscale circulations in quasilinear convective systems are becoming more readily observable in warning environments due to the improved availability of real-time radar data at higher spatial and temporal resolutions. These circulations are frequently associated with narrow paths of enhanced wind damage, particularly when combined with a fast system motion.

Some of these circulations have been observed to grow in size and/or intensity, and some last longer than others. It is a significant challenge to anticipate in real-time where circulations might develop along the line, which nascent circulations might intensify enough to produce swaths of enhanced wind damage, and which circulations will quickly dissipate.

In a storm environment capable of producing significant misoscale circulations, this presents a major dilemma regarding Tornado Warning services. Large, long duration Tornado Warnings to cover all possible tornadic circulations in a quasilinear system have potentially negative societal implications, setting into motion widespread protective and emergency response actions for, at the most, very isolated impacts. On the other hand, while a few of these circulations might intensify enough to be classified as tornadoes, by the time one is detected and a warning disseminated, the threat is usually over.

This presentation will show archived examples of misoscale circulations in quasilinear convective systems of various sizes, durations, and intensities, to illustrate the wide range of events observed. The discussion will focus on the difficulty in classifying these events as tornadic vs. non-tornadic, the challenge in anticipating transient tornadic circulations among the many weaker circulations, and the dilemma facing forecasters when deciding whether to issue a Tornado Warning during these events. The presentation will conclude with recommendations for effective warning services during such events.

Available online at http://ams.confex.com/ams/25SLS/techprogram/paper_176213.htm.

Schwartz, C. S., J. S. Kain, S. J. Weiss, M. Xue, D. R. Bright, F. Kong, K. W. Thomas, J. J. Levit, M. C. Coniglio, 2009: Next-day convection-allowing WRF model guidance: A second look at 2 vs. 4 km grid spacing. Monthly Weather Review, 137, 3351-3372.

During the 2007 NOAA Hazardous Weather Testbed (HWT) Spring Experiment, the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma produced convection-allowing forecasts from a single deterministic 2 km model and a 10-member 4 km resolution ensemble. In this study, the 2 km deterministic output was compared with forecasts from the 4 km ensemble control member. Other than the difference in horizontal resolution, the two sets of forecasts featured identical WRFARW configurations, including vertical resolution, forecast domain, initial and lateral boundary conditions, and physical parameterizations. Therefore, forecast disparities were attributed solely to differences in horizontal grid spacing.

This study is a follow-up to similar work that was based on results from the 2005 Spring Experiment. Unlike the 2005 Experiment, however, model configurations were more rigorously controlled in the present study, providing a more robust dataset and a cleaner isolation of the dependence on horizontal resolution. Additionally, in this study, the 2 and 4 km output were compared to 12 km forecasts from the North American Mesoscale (NAM) model.

Model forecasts were analyzed using objective verification of mean hourly precipitation and visual comparison of individual events, primarily during the 21- to 33-hour forecast period to examine the utility of the models as next-day guidance. On average, both the 2 and 4 km model forecasts showed substantial improvement over the 12 km NAM. However, although the 2 km forecasts produced more detailed structures on the smallest resolvable scales, the patterns of convective initiation, evolution, and organization were remarkably similar to the 4 km output. Moreover, on average, metrics such as equitable threat score, frequency bias, and fractions skill score revealed no statistical improvement of the 2 km forecasts compared to the 4 km forecasts. These results, based on the 2007 dataset, corroborate previous findings, suggesting that decreasing horizontal grid spacing from 4 to 2 km provides little added value as next-day guidance for severe convective storm and heavy rain forecasters in the United States.

Schwartz, C. S., J. S. Kain, S. J. Weiss, D. R. Bright, M. Xue, F. Kong, K. W. Thomas, J. J. Levit, M. C. Coniglio, 2008: Next-day convection-allowing WRF model guidance: A second look at 2- vs. 4-km grid spacing. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, P10.3. [Available from Jack Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142052.htm.

Schwartz, C. S., J. S. Kain, D. R. Bright, S. J. Weiss, M. Xue, F. Kong, J. J. Levit, M. C. Coniglio, M. S. Wandishin, 2008: Toward improved convection-allowing ensembles: Model physics sensitivities and optimizing probabilistic guidance with small ensemble membership. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 13A.6. [Available from Jack Kain, NSSL, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142048.htm.

Schwartz, C. S., J. S. Kain, D. R. Bright, S. J. Weiss, M. Xue, F. Kong, J. J. Levit, M. C. Coniglio, M. S. Wandishin, 2009: Optimizing probabilistic high resolution ensemble guidance for hydrologic prediction. Preprints, 23rd Conference on Hydrology, Phoenix, AZ, USA, Amer. Meteor. Soc., CD-ROM, 9.4.

Available online at http://ams.confex.com/ams/89annual/techprogram/paper_147171.htm.

Schwartz, C. S., J. S. Kain, M. C. Coniglio, S. J. Weiss, D. R. Bright, M. Xue, F. Kong, K. W. Thomas, M. S. Wandishin, 2010: Toward Improved Convection-Allowing Ensembles: Model Physics Sensitivities and Optimizing Probabilistic Guidance with Small Ensemble Membership. Weather and Forecasting, 25, 263-280.

During the 2007 NOAA Hazardous Weather Testbed Spring Experiment, the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma produced a daily 10-member 4-km horizontal resolution ensemble forecast covering approximately three-fourths of the continental United States. Each member used the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) model core, which was initialized at 2100 UTC, ran for 33 h, and resolved convection explicitly. Different initial condition (IC), lateral boundary condition (LBC), and physics perturbations were introduced in 4 of the 10 ensemble members, while the remaining 6 members used identical ICs and LBCs, differing only in terms of microphysics (MP) and planetary boundary layer (PBL) parameterizations. This study focuses on precipitation forecasts from the ensemble.

The ensemble forecasts reveal WRF-ARW sensitivity to MP and PBL schemes. For example, over the 7-week experiment, the Mellor–Yamada–Janjić PBL and Ferrier MP parameterizations were associated with relatively high precipitation totals, while members configured with the Thompson MP or Yonsei University PBL scheme produced comparatively less precipitation. Additionally, different approaches for generating probabilistic ensemble guidance are explored. Specifically, a “neighborhood” approach is described and shown to considerably enhance the skill of probabilistic forecasts for precipitation when combined with a traditional technique of producing ensemble probability fields.

Sobash, R. A., D. R. Bright, A. R. Dean, J. S. Kain, M. C. Coniglio, S. J. Weiss, J. J. Levit, 2008: Severe storm forecast guidance based on explicit identification of convective phenomena in WRF-model forecasts. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 11.3.

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142187.htm.

Sobash, R. A., J. S. Kain, D. R. Bright, A. R. Dean, M. C. Coniglio, S. J. Weiss, J. J. Levit, 2009: Forecast guidance for severe thunderstorms based on identification of extreme phenomena in convection-allowing model forecasts. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 4B.6.

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154328.htm.

Stensrud, D. J., N. Yussouf, D. C. Dowell, M. C. Coniglio, 2009: Assimilating surface data into a mesoscale model ensemble: Cold pool analyses from spring 2007. Atmos. Res., 93, 207-220.

Hourly mesoscale analyses are created through an ensemble Kalman filter assimilation of 2-m potential temperature, 2-m dewpoint temperature, and 10-m wind observations into the Weather Research and Forecast (WRF-ARW) model using the Data Assimilation Research Testbed (DART) framework. Hourly analyses are created from 1300 UTC to 0600 UTC each day from 15 March through 30 June 2007. Two cases in which a distinct isolated mesoscale convective system is seen in observations are selected for further examination. Results indicate that the ensemble mean surface analyses reproduce the surface mesoscale features associated with cold pools underneath these precipitating systems in agreement with available observations. However, the ensemble Kalman filter also is able to produce vertical motion fields and vertical structures within and above the boundary layer that are consistent with these observed surface features. In particular, a rear inflow jet is produced at roughly 1 km above ground level behind the main convective line along with an “onion” sounding along the back edge of the trailing stratiform precipitation region near a surface mesolow. Both of these structures are known to be associated with MCSs and the ability of the ensemble Kalman filter assimilation to produce these important mesoscale features is encouraging.

Stolzenburg, M., T. C. Marshall, W. D. Rust, E. Bruning, D. R. MacGorman, T. Hamlin, 2007: Electric field values observed near lightning flash initiations. Geophysical Research Letters, 34, L04804-L04804.

From a dataset of about 250 soundings of electric field (E), nine were adversely affected by lightning. These soundings are interpreted as ending near lightning initiation locations. Scaled to standard pressure, the largest observed E was 626 kV m−1 and the largest estimated E was 929 kV m−1. E exceeded runaway breakdown threshold, RBth, by factors of 1.1–3.3 before each flash, and overvoltages were 1.4–4.3. Seven cases had rapid E increases (rates of 11–100 kV m−1 s−1) in the few seconds before the flash, and in three the maximum E occurred 3 s or more before the flash. A tenth sounding with E > RBth for 38 s had subsequent lightning initiate 2 km from the balloon; one channel came within 400 m, but the flash and large E did not adversely affect the instruments. The findings suggest that E > RBth is a necessary condition for lightning initiation, but it is not sufficient.

Available online at http://www.agu.org/pubs/crossref/2007/2006GL028777.shtml.

Stuart, N. A., P. S. Market, B. Telfeyan, G. M. Lackmann, K. Carey, H. E. Brooks, B. C. Motta, K. Reeves, 2006: The future of humans in an increasingly automated forecast process. Bulletin of the American Meteorological Society, 87, 1-6.

The meteorological community is considering new roles for forecasters as increased accuracy in computer-generated weather forecasts continues to reduce the need for human intervention.

Available online at http://www.nssl.noaa.gov/users/brooks/public_html/papers/stuart.pdf.

Suarez, A., H. D. Reeves, D. Wheatley, M. Coniglio, 2012: Comparison of Ensemble Kalman Filter–Based Forecasts to Traditional Ensemble and Deterministic Forecasts for a Case Study of Banded Snow. Weather and Forecasting, 27, 85-105.

The ensemble Kalman filter (EnKF) technique is compared to other modeling approaches for a case study of banded snow. The forecasts include a 12- and 3-km grid-spaced deterministic forecast (D12 and D3), a 12-km 30-member ensemble (E12), and a 12-km 30-member ensemble with EnKF-based four- dimensional data assimilation (EKF12). In D12 and D3, flow patterns are not ideal for banded snow, but they have similar precipitation accumulations in the correct location. The increased resolution did not improve the quantitative precipitation forecast. The E12 ensemble mean has a flow pattern favorable for banding and precipitation in the approximate correct location, although the magnitudes and probabilities of relevant features are quite low. Six members produced good forecasts of the flow patterns and the precipitation structure. The EKF12 ensemble mean has an ideal flow pattern for banded snow and the mean produces banded precipitation, but relevant features are about 100 km too far north. The EKF12 has a much lower spread than does E12, a consequence of their different initial conditions. Comparison of the initial ensemble means shows that EKF12 has a closed surface low and a region of high low- to midlevel humidity that are not present in E12. These features act in concert to produce a stronger ensemble-mean cyclonic system with heavier precipitation at the time of banding.

Available online at http://dx.doi.org/10.1175/WAF-D-11-00030.1.

Trapp, R. J., N. S. Diffenbaugh, H. E. Brooks, M. E. Baldwin, E. D. Robinson, J. S. Pal, 2007: Changes in severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing. Proceedings of the National Academy of Sciences of the United States of America, 104, 19723.

Severe thunderstorms comprise an extreme class of deep convective clouds and produce high-impact weather such as destructive surface winds, hail, and tornadoes. This study addresses the question of how severe thunderstorm frequency in the United States might change because of enhanced global radiative forcing associated with elevated greenhouse gas concentrations. We use global climate models and a high-resolution regional climate model to examine the larger-scale (or "environmental") meteorological conditions that foster severe thunderstorm formation. Across this model suite, we find a net increase during the late 21st century in the number of days in which these severe thunderstorm environmental conditions (NDSEV) occur. Attributed primarily to increases in atmospheric water vapor within the planetary boundary layer, the largest increases in NDSEV are shown during the summer season, in proximity to the Gulf of Mexico and Atlantic coastal regions. For example, this analysis suggests a future increase in NDSEV of 100% or more in locations such as Atlanta, GA, and New York, NY. Any direct application of these results to the frequency of actual storms also must consider the storm initiation.

Van Cooten, S., K. E. Kelleher, K. W. Howard, J. Zhang, J. J. Gourley, J. S. Kain, K. Nemunaitis-Monroe, A. Arthur, C. Langston, Z. Flamig, H. Moser, . et al., 2011: The CI-FLOW Project: A System for Total Water Level Prediction from the Summit to the Sea. Bulletin of the American Meteorological Society, 92, 1427-1442.

The objective of the Coastal and Inland Flooding Observation and Warning (CI-FLOW) project is to prototype new hydrometeorologic techniques to address a critical NOAA service gap: routine total water level predictions for tidally influenced watersheds. Since February 2000, the project has focused on developing a coupled modeling system to accurately account for water at all locations in a coastal watershed by exchanging data between atmospheric, hydrologic, and hydrodynamic models. These simulations account for the quantity of water associated with waves, tides, storm surge, rivers, and rainfall, including interactions at the tidal/surge interface.

Within this project, CI-FLOW addresses the following goals: i) apply advanced weather and oceanographic monitoring and prediction techniques to the coastal environment; ii) prototype an automated hydrometeorologic data collection and prediction system; iii) facilitate interdisciplinary and multiorganizational collaborations; and iv) enhance techniques and technologies that improve actionable hydrologic/hydrodynamic information to reduce the impacts of coastal flooding. Results are presented for Hurricane Isabel (2003), Hurricane Earl (2010), and Tropical Storm Nicole (2010) for the Tar–Pamlico and Neuse River basins of North Carolina. This area was chosen, in part, because of the tremendous damage inflicted by Hurricanes Dennis and Floyd (1999). The vision is to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds.

Available online at http://journals.ametsoc.org/doi/pdf/10.1175/2011BAMS3150.1.

Van Cooten, S., K. Kelleher, K. Howard, J. Zhang, J. J. Gourley, C. Langston, V. Farmer, K. Monroe, Z. L. Flamig, H. Moser, R. Kolar, Y. Hong, K. Dresback, E. Tromble, H. Vergara, R. Luettich, B. Blanton, K. Galuppi, C. A. Blain, J. F. Thigpen, K. Mosher, D. Figursky, M. Moneypenny, J. Orrock, R. Bandy, C. Goodall, J. Kelley, J. Greenlaw, M. Wengren, D. Eslinger, J. Payne, J. Feldt, J. Schmidt, T. Hamill, R. H. Bacon, R. Stickney, L. Spence, 2011: Coastal and Inland FLooding Observation and Warning (CI-FLOW) Project-An Assesment of Research Outcomes From An Integrated Hydrologic Prediction System for Coastal Watersheds. Preprints, 25th Conference on Hydrology, Seattle, WA, USA, American Meteorological Society, 7.4.

The objective of the Coastal and Inland FLooding Observation and Warning (CI-FLOW) project is to develop and prototype new hydrometeorological techniques to address a critical NOAA service gap: routine total water level predictions for tidally-influenced watersheds. Since February 2000, the project has focused on developing a system to accurately account for water at all locations in a coastal watershed. The CI-FLOW computing framework interactively exchanges data between atmospheric, river, and ocean models to produce water quantity simulations upstream and downstream of the tidal plain, including shorelines. These simulations account for the quantity of water associated with waves, tides, storm surge, rivers, and rainfall, inclusive of interactions at the tidal/surge interface.

Within this framework, CI-FLOW accomplishes the following goals: 1) apply advanced weather monitoring and prediction techniques to the coastal environment; 2) prototype an automated hydrometeorological data collection and prediction system; 3) facilitate interdisciplinary and multi-organizational collaborations; and 4) enhance techniques and technologies that improve actionable hydrologic information to reduce the impacts of coastal floods/flash floods. Results are presented for Hurricane Isabel, the first test of the integrated framework, for the Tar-Pamlico and Neuse river basins of North Carolina. This area was chosen, in part, because of the tremendous damage inflicted by Hurricanes Dennis and Floyd in September 1999. However, the vision is to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds

Available online at http://ams.confex.com/ams/91Annual/flvgateway.cgi/id/17363?recordingid=17363.

Vasiloff, S. V., D. J. Seo, K. W. Howard, J. Zhang, D. H. Kitzmiller, M. G. Mullusky, W. F. Krajewski, E. A. Brandes, R. M. Rabin, D. S. Berkowitz, H. E. Brooks, J. A. McGinley, R. J. Kuligowski, B. G. Brown, 2007: Improving QPE and Very Short Term QPF: An Initiative for a Community-Wide Integrated Approach. Bulletin of the American Meteorological Society, 88, 1899-1911.

Accurate quantitative precipitation estimates (QPE) and very short term quantitative precipitation forecasts (VSTQPF) are critical to accurate monitoring and prediction of water-related hazards and water resources. While tremendous progress has been made in the last quarter-century in many areas of QPE and VSTQPF, significant gaps continue to exist in both knowledge and capabilities that are necessary to produce accurate high-resolution precipitation estimates at the national scale for a wide spectrum of users. Toward this goal, a national next-generation QPE and VSTQPF (Q2) workshop was held in Norman, Oklahoma, on 28–30 June 2005. Scientists, operational forecasters, water managers, and stakeholders from public and private sectors, including academia, presented and discussed a broad range of precipitation and forecasting topics and issues, and developed a list of science focus areas. To meet the nation's needs for the precipitation information effectively, the authors herein propose a community-wide integrated approach for precipitation information that fully capitalizes on recent advances in science and technology, and leverages the wide range of expertise and experience that exists in the research and operational communities. The concepts and recommendations from the workshop form the Q2 science plan and a suggested path to operations. Implementation of these concepts is expected to improve river forecasts and flood and flash flood watches and warnings, and to enhance various hydrologic and hydrometeorological services for a wide range of users and customers. In support of this initiative, the National Mosaic and Q2 (NMQ) system is being developed at the National Severe Storms Laboratory to serve as a community test bed for QPE and VSTQPF research and to facilitate the transition to operations of research applications. The NMQ system provides a real-time, around-the-clock data infusion and applications development and evaluation environment, and thus offers a community-wide platform for development and testing of advances in the focus areas.

Vera, C., J. Beaz, M. Douglas, C. Emmanuel, J. Marengo, J. Meitin, M. Nicolini, J. Nouges-Paegle, J. Paegle, O. Penalba, P. Salio, C. Saulo, M. A. Silva-Dias, P. Silva-Dias, E. Zipser, 2006: The South American Low-Level Jet Experiment. Bulletin of the American Meteorological Society, 87, 63-77.

Verbout, S. M., H. E. Brooks, L. M. Leslie, D. M. Schultz, 2006: Evolution of the U.S. tornado database: 1954-2004. Weather and Forecasting, 21, 86-93.

Over the last 50 yr, the number of tornadoes reported in the United States has doubled from about 600 per year in the 1950s to around 1200 in the 2000s. This doubling is likely not related to meteorological causes alone. To account for this increase a simple least squares linear regression was fitted to the annual number of tornado reports. A "big tornado day" is a single day when numerous tornadoes and/or many tornadoes exceeding a specified intensity threshold were reported anywhere in the country. By defining a big tornado day without considering the spatial distribution of the tornadoes, a big tornado day differs from previous definitions of outbreaks. To address the increase in the number of reports, the number of reports is compared to the expected number of reports in a year based on linear regression. In addition, the F1 and greater Fujita-scale record was used in determining a big tornado day because the F1 and greater series was more stationary over time as opposed to the F2 and greater series. Thresholds were applied to the data to determine the number and intensities of the tornadoes needed to be considered a big tornado day. Possible threshold values included fractions of the annual expected value associated with the linear regression and fixed numbers for the intensity criterion. Threshold values of 1.5% of the expected annual total number of tornadoes and/or at least 8 F1 and greater tornadoes identified about 18.1 big tornado days per year. Higher thresholds such as 2.5% and/or at least 15 F1 and greater tornadoes showed similar characteristics, yet identified approximately 6.2 big tornado days per year. Finally, probability distribution curves generated using kernel density estimation revealed that big tornado days were more likely to occur slightly earlier in the year and have a narrower distribution than any given tornado day.

Available online at http://www.cimms.ou.edu/~schultz/pubs/verboutetal06.pdf.

Verbout, S. M., D. M. Schultz, L. M. Leslie, H. E. Brooks, D. J. Karoly, K. L. Elmore, 2007: Tornado outbreaks associated with landfalling hurricanes in the north Atlantic Basin: 1954–2004. Meteorology and Atmospheric Physics, 97, 255-271.

Tornadoes are a notable potential hazard associated with landfalling hurricanes. The purpose of this paper is to discriminate hurricanes that produce numerous tornadoes (tornado outbreaks) from those that do not (nonoutbreaks). The data consists of all hurricane landfalls that affected the United States from the North Atlantic basin from 1954 to 2004 and the United States tornado record over the same period. Because of the more than twofold increase in the number of reported tornadoes over these 51 years, a simple least-squares linear regression ("the expected number of tornadoes") was fit to the annual number of tornado reports to represent a baseline for comparison.

The hurricanes were sorted into three categories. The first category, outbreak hurricanes, was determined by hurricanes associated with the number of tornado reports exceeding a threshold of 1.5% of the annual expected number of tornadoes and at least 8 F1 and greater tornadoes during the time of landfall (from outer rainbands reaching shore to dissipation of the system). Eighteen hurricane landfalls were classified as outbreak hurricanes. Second, 37 hurricanes having less han 0.5% of the annual expected number of tornadoes were classified as nonoutbreak landfalls. Finally, 28 hurricanes that were neither outbreak nor nonoutbreak hurricanes were classified as midclass hurricane landfalls.

Stronger hurricanes are more likely to produce tornado outbreaks than weaker hurricanes. While 78% of outbreak hurricanes were category 2 or greater at landfall, only 32% of nonoutbreak hurricanes were category 2 or greater at landfall. Hurricanes that made landfall along the southern coast of the United States and recurved northeastward were more likely to produce tornadoes than those that made landfall along the east coast or those that made landfall along the southern coast but did not recurve. Recurvature was associated with a 500-hPa trough in the jet stream, which also contributed to increased deep-layer shear through the hurricane, favoring mesocyclogenesis, and increased the low-level shear, favoring tornadogenesis. The origin of the hurricane, date of landfall, and El Niño-Southern Oscillation phase do not appear to be factors in outbreak hurricane creation. The results of this study help clarify inconsistencies in the previous literature regarding tornado occurrences in landfalling hurricanes.

Available online at http://www.springerlink.com/content/8132257282886516/fulltext.pdf.

Vich, M., R. Romero, H. E. Brooks, 2011: Ensemble prediction of Mediterranean high-impact events using potential vorticity perturbations. Part I: Comparison against the multiphysics approach. Atmospheric Research, 102, 227-241.

The western Mediterranean is a very cyclogenetic area and many of the cyclones developed over this region are associated with high-impact weather phenomena that affect the society of the coastal countries. Two ensemble prediction systems (EPSs) based on multiphysics and perturbed initial and boundary conditions (IBC) are designed in order to improve the forecast of these heavy rain episodes. The MM5 mesoscale model nested in the ECMWF forecast fields provides the simulations, run at 22.5 km resolution for a two-day period.

The multiphysics ensemble combines different model physical parameterization schemes while the other ensemble perturbs the initial state and boundary forcing of the model with the
aid of a PV inversion scheme. A PV error climatology derived from the large-scale fields allows to perturb the ECMWF PV fields using the appropriate error range.

The verification procedure indicates that even though both EPSs are skillful, the perturbed IBC ensemble is more proficient than the multiphysics EPS for the 19 Mediterranean cyclonic events with heavy rain considered in the study. Therefore the results show a more dominant role of the uncertainties in the initial and boundary conditions than the model error, although both of them contribute significantly to improve the predictability of Western Mediterranean high impact weather situations.

Ware, E. C., D. M. Schultz, H. E. Brooks, P. J. Roebber, S. L. Bruening, 2006: Improving snowfall forecasting by accounting for the climatological variability of snow density. Weather and Forecasting, 21, 94-103.

Accurately forecasting snowfall is a challenge. In particular, one poorly understood component of snowfall forecasting is determining the snow ratio. The snow ratio is the ratio of snowfall to liquid equivalent and is inversely proportional to the snow density. In a previous paper, an artificial neural network was developed to predict snow ratios probabilistically in three classes: heavy (1:1 < ratio < 9:1), average (9:1 <= ratio <= 15:1), and light (ratio > 15:1). A Web-based application for the probabilistic prediction of snow ratio in these three classes based on operational forecast model soundings and the neural network is now available. The goal of this paper is to explore the statistical characteristics of the snow ratio to determine how temperature, liquid equivalent, and wind speed can be used to provide additional guidance (quantitative, wherever possible) for forecasting snowfall, especially for extreme values of snow ratio. Snow ratio tends to increase as the low-level (surface to roughly 850 mb) temperature decreases. For example, mean low-level temperatures greater than −2.7°C rarely (less than 5% of the time) produce snow ratios greater than 25:1, whereas mean low-level temperatures less than −10.1°C rarely produce snow ratios less than 10:1. Snow ratio tends to increase strongly as the liquid equivalent decreases, leading to a nomogram for probabilistic forecasting snowfall, given a forecasted value of liquid equivalent. For example, liquid equivalent amounts 2.8–4.1 mm (0.11–0.16 in.) rarely produce snow ratios less than 14:1, and liquid equivalent amounts greater than 11.2 mm (0.44 in.) rarely produce snow ratios greater than 26:1. The surface wind speed plays a minor role by decreasing snow ratio with increasing wind speed. Although previous research has shown simple relationships to determine the snow ratio are difficult to obtain, this note helps to clarify some situations where such relationships are possible.

Available online at http://www.cimms.ou.edu/~schultz/pubs/wareetal06.pdf.

Watts, C. J., R. L. Scott, J. Garatuza-Payan, J. C. Rodriguez, J. H. Prueger, W. P. Kustas, M. Douglas, 2007: Changes in Vegetation Condition and Surface Fluxes during NAME 2004. Journal of Climate, 20, .

Weiss, S. J., J. S. Kain, D. R. Bright, J. J. Levit, M. Pyle, Z. I. Janjic, B. Ferrier, J. Du, M. L. Weisman, M. Xue, 2007: The NOAA Hazardous Weather Testbed: Collaborative testing of ensemble and convection-allowing WRF models and subsequent transfer to operations at the Storm Prediction Center.. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 6B.4.

Weiss, S. J., J. S. Kain, D. R. Bright, J. J. Levit, M. Pyle, Z. I. Janjic, B. S. Ferrier, J. Du, M. L. Weisman, M. Xue, 2007: The NOAA Hazardous Weather Testbed: Collaborative testing of ensemble and convection-allowing WRF models and subsequent transfer to operations at the Storm Prediction Center. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, Amer. Mete. [Available from S. J. Weiss, SPC, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

Since 2003, the Storm Prediction Center (SPC) has played a leading role in testing various configurations of Short-Range Ensemble Forecast (SREF) systems and high resolution WRF models for their operational utility. These test and evaluation activities have occurred during organized collaborative activities in the NOAA Hazardous Weather Testbed (HWT) in Norman. The HWT is designed to bring research scientists, model developers, and forecasters together to work on issues of mutual interest, facilitating the rapid transfer of research to operations. This organizational framework helps researchers and model developers to better understand the operational challenges and requirements of forecasters, educates forecasters on new science and technological advances, and has accelerated the application of new modeling approaches to severe weather forecasting. This paper focuses on the use of the operational NCEP SREF and two experimental high resolution convection-allowing WRF models as complementary sources of information for SPC forecasters.

NCEP is running a 21 member multi-model, multi-analysis SREF system with enhanced physics diversity four times daily with output through 87 hours. SPC processes the grids from all SREF members and produces a large variety of products for severe weather forecasting, including standard spaghetti, mean and spread, probability, and max/min charts, as well as specialized multi-parameter convective fields and post-processed calibrated probabilities for the occurrence of thunderstorms, dry thunderstorms, and severe thunderstorms.

NCEP has also been running an experimental high resolution WRF-Non-hydrostatic Mesoscale Model (WRF-NMM4) for the SPC since April 2004; this model was recently upgraded to a 4 km grid length. And starting in November 2006, SPC forecasters have had access to output from a 4 km Advanced Research WRF (WRF-ARW4) developed by NCAR and run at the National Severe Storms Laboratory. Both WRF models are initialized from a cold start once daily at 0000 UTC using initial and lateral boundary conditions from the operational North American Mesoscale model, and provide forecasts through a 36 hour period over a domain covering approximately three-fourths of the U.S. Several unique WRF products have been developed for use by severe weather forecasters, including simulated reflectivity and measures of updraft rotation in model-generated storms.

The incorporation of SREF and high resolution WRF guidance into an operational severe weather forecasting environment already dealing with high volumes of observational and model data requires careful assessment of the unique strengths of each modeling system, and knowledge of the specific needs of SPC forecasters. Since the SPC severe weather forecast mission focuses on phenomena smaller than that predicted by mesoscale models, such as tornadoes and severe thunderstorms, the traditional forecast methodology has focused on first predicting the evolution of the mesoscale environment and then determining the spectrum of convective storms a particular environment may support. SREF output has been found to be particularly useful in quantifying the likelihood that the environment will occupy specific parts of convective parameter space, as well as the likelihood and timing for thunderstorms and severe thunderstorms to develop over Outlook-scale regions. While this can be extremely helpful to SPC forecasters, more detailed information about the intensity and mode of storms is also needed, since the type of severe weather (e.g., tornadoes, damaging wind) is often strongly related to convective mode. The value of the high resolution WRF guidance is most evident here, as it has capability to resolve near storm-scale convective characteristics, such as the development of discrete cells ahead of a line of storms, and the development of model storms with rotating updrafts.

We will examine the complementary role of SREF and high resolution WRF output during several strongly-forced and weakly-forced severe weather days during the winter and spring severe weather period and illustrate the operational application of these model datasets in the SPC decision-making process for both Convective Outlooks and Watches.

Available online at http://ams.confex.com/ams/pdfpapers/124772.pdf.

Wen, Y., Y. Hong, G. Zhang, T. J. Schuur, J. J. Gourley, Z. Flamig, K. Morris, Q. Cao, 2011: Cross validation of spaceborne radar and ground polarimetric radar aided by polarimetric echo classification of hydrometeor types. Journal of Applied Meteorology and Climatology, 50, 1389-1402.

Wulfmeyer, V., A. Behrendt, C. Kottmeier, U. Corsmeier, C. Barthlott, G. C. Craig, M. Hagen, D. Althausen, F. Aoshima, M. Arpagaus, H. S. Bauer, L. Bennett, A. Blyth, C. Brandau, C. Champollion, S. Crewell, G. Dick, P. DiGirolamo, M. Dorninger, Y. Dufournet, R. Eigenmann, R. Engelmann, C. Flamant, T. Foken, T. Gorgas, M. Grzeschik, J. Handwerker, C. Hauck, H. Hoeller, W. Junkermann, N. Kalthoff, C. Kiemle, S. Klink, M. Koenig, L. Krauss, C. N. Long, F. Madonna, S. Mobbs, B. Neiniger, S. Pal, G. Peters, G. Pigeon, E. Richard, M. W. Rotach, H. Russchenberg, T. Schwitalla, V. Smith, R. Steinacker, J. Trentmann, D. D. Turner, J. van Baelen, S. Vogt, H. Volkert, T. Weckwerth, H. Wernli, A. Wieser, M. Wirth, 2011: The convective and orographically induced precipitation study (COPS): The scientific strategy, the field phase, and first highlights.. Quarterly Journal of the Royal Meteorological Society, 137, 3-30.

Within the framework of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote-sensing systems such as the Global Positioning System as well as a synergy of multi-wavelength passive and active remote-sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen Intensive Observation Periods with 37 operation days and eight additional Special Observation Periods were performed, providing a comprehensive data set covering different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations, and in the performance of ensembles of convection-permitting models in complex terrain.

Xue, M., F. Kong, D. Weber, K. W. Thomas, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. S. Wandishin, M. C. Coniglio, J. Du, 2007: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment.. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.1.

Xue, M., F. Kong, D. B. Weber, K. W. Thomas, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. S. Wandishin, M. C. Coniglio, J. Du, 2007: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2007 Spring Experiment. Preprints, 22th Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction, Park City, UT, USA, Amer. Meteor. Soc., CD-ROM, 3B.1. [Available from Ming Xue, CAPS, 120 David L. Boren Blvd, Norman, OK, USA, 73072.]

As a continuation of past collaborations with the NOAA Hazardous Weather Testbed (HWT), the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma will produce daily 10-member 4-km-resolution ensemble forecasts during the spring of 2007, as contributions to the HWT 2007 Spring Experiment. At the same time, a single 2-km deterministic forecast will be produced over the same domain that covers two thirds of the continental US. The forecasts will start from 2100 UTC and extend to 0600 UTC of the third day for a total length of 33 hours. The experiment will start in mid-April and last for about 2 months.

The CAPS effort in 2007 will use the WRF ARW model and the ensemble will include both initial/boundary condition and physics perturbations. The initial and boundary condition perturbations will come from the NCEP 2100 UTC SREF forecast cycle, with the control-member initial condition coming from the NAM 2100 UTC analysis on the 12 km grid. The physics perturbation members are designed for easy identification of the strengths and weakness of leading microphysics and PBL schemes within WRF.

Selected data fields will be fed directly into the NAWIPS systems in the HWT for use by experimental forecast and evaluation teams in the Spring Experiment. These will be combined with separate deterministic WRF forecasts at 3 km grid spacing, contributed by NCAR and EMC. Additional data fields from the CAPS runs will be posted on the web in realtime for external verification purposes. These include side by side comparisons of 2-km forecast composite reflectivity with the NSSL national reflectivity mosaic at 5-minute intervals and graphical displays of a large array of 2-D fields and ensemble products, including postage stamps and probability maps

Over 1000 CPUs at the Pittsburgh Supercomputing Center (PSC) will be used to produce the forecasts while additional processors at the University of Oklahoma Supercomputing Center for Education and Research (OSCER) will be used for post-processing. A special super-high-speed link capable of 200 MB/s will be set up between PSC and OSCER for data transfer.

Results of realtime forecasts and preliminary retrospective analysis on selected cases will be presented at the conference.

Available online at http://ams.confex.com/ams/pdfpapers/124587.pdf.

Xue, M., F. Kong, K. W. Thomas, J. Gao, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2009: CAPS realtime 4 km multi-model convection-allowing ensemble and 1 km convection-resolving forecasts for the NOAA Hazardous Weather Testbed 2009 Spring Experiment. Preprints, 23rd Conference on Weather Analysis and Forecasting/19th Conference on Numerical Weather Prediction, Omaha, NE, USA, Amer. Meteor. Soc., CD-ROM, 16A.2.

Available online at http://ams.confex.com/ams/23WAF19NWP/techprogram/paper_154323.htm.

Xue, M., F. Kong, K. W. Thomas, J. Gao, Y. Wang, K. Brewster, K. K. Droegemeier, J. S. Kain, S. J. Weiss, D. R. Bright, M. C. Coniglio, J. Du, 2008: CAPS realtime storm-scale ensemble and high-resolution forecasts as part of the NOAA Hazardous Weather Testbed 2008 Spring Experiment. Preprints, 24th Conference on Severe Local Storms, Savannah, GA, USA, Amer. Meteor. Soc., CD-ROM, 12.2.

Available online at http://ams.confex.com/ams/24SLS/techprogram/paper_142036.htm.

Yu, T. Y., A. B. Chalamalasetti, R. J. Doviak, D. S. Zrnic, 2006: Resolution Enhancement Technique using Range Oversampling. Journal of Atmospheric and Oceanic Technology, 23, 228-240.

Zipser, E. J., C. H. Twohy, S. C. Tsay, K. L. Thornhill, S. Tanelli, R. Ross, T. N. Krishnamurti, Q. Ji, G. Jenkins, S. Ismail, N. C. Hsu, R. Hood, G. M. Heymsfield, A. Heymsfield, J. Halvorson, H. M. Goodman, R. Ferrare, J. P. Dunion, M. Douglas, R. Cifelli, G. Chen, E. V. Browell, B. Anderson, 2009: The Saharan Air Layer and the Fate of African Easterly Waves - NASA's AMMA 2006 Field Study of Tropical Cyclogenesis. Bulletin of the American Meteorological Society, 90, 1137-1156.

In 2006, NASA led a field campaign to investigate the factors that control the fate of African easterly waves (AEWs) moving westward into the tropical Atlantic Ocean. Aircraft and surface-based equipment were based on Cape Verde's islands, helping to fill some of the data void between Africa and the Caribbean. Taking advantage of the international African Monsoon Multidisciplinary Analysis (AMMA) program over the continent, the NASA–AMMA (NAMMA) program used enhanced upstream data, whereas NOAA aircraft farther west in the Atlantic studied several of the storms downstream. Seven AEWs were studied during AMMA, with at least two becoming tropical cyclones. Some of the waves that did not develop while being sampled near Cape Verde likely intensified in the central Atlantic instead. NAMMA observations were able to distinguish between the large-scale wave structure and the smaller-scale vorticity maxima that often form within the waves. A special complication of the east Atlantic environment is the Saharan air layer (SAL), which frequently accompanies the AEWs and may introduce dry air and heavy aerosol loading into the convective storm systems in the AEWs. One of the main achievements of NAMMA was the acquisition of a database of remote sensing and in situ observations of the properties of the SAL, enabling dynamic models and satellite retrieval algorithms to be evaluated against high-quality real data. Ongoing research with this database will help determine how the SAL influences cloud micro-physics and perhaps also tropical cyclogenesis, as well as the more general question of recognizing the properties of small-scale vorticity maxima within tropical waves that are more likely to become tropical cyclones.